Alright, aside from what enigma213 and rmmr111 said, I'd like to stress that this image is very pixelated. It looks like you enlarged both the stock image and the character to make the higher resolutions of this wallpaper. Of all of them, 1280x720 is the only good one in that aspect, with the least amount of (noticeable) pixelation. And working with stock images as textures is OK, but in this case it really is "too much". I can see the idea you were going for and it's not a bad one at all, but the execution is lacking. For example, if the girl were encased in ice, she'd have a more bluish/white look (from the way the light falls through the ice). In short:

1. Don't abuse textures. Less is more sometimes.

2. Don't enlarge small stock images just so you can make big resolutions. Learn to vector/clean smaller images if you want to do so.

Again, the composition is pretty good and I understand what you were trying to do here, but the way you did it can certainly be improved. Look up tutorials and check out others' wallpapers, because you're already on the right track and your technique only needs a bit of fixing to be truly good :) Good luck on your future projects!

Like others have noted, the perspective is kind of strange, but not because of the angle at which Rei is diving (she could be swimming sideways -possible, although it looks strange). IMO, it's because of three things:

1) the way the floor tiles connect to the wall tiles: should be a straight line. If you were going for a more unusual tile scheme, you'd usually need to show more of the pool floor to prevent the pattern from looking awkward (like here). If so, it'd need an even more forced perspective on the floor, maybe a circular-looking tile placement - even though the tiles themselves aren't placed in a circle (hey, forced perspective).

2) the pattern and sizes of the tiles on the wall and the tiles on the floor are too different.

3) the tiles on the floor should be even smaller where they connect to the wall. To know how small you should make them, take a look at Rei's arms, they're an excellent indicator of the general perspective your wall should have.

Aside from the perspective, it's good that you provided a texture-less version (IMO, the grainy texture doesn't fit such a smooth-looking environment), but the lines of the vector are very jagged. Either work with slightly more blurry outlines, use anti-aliasing on the Pen Tool or avoid placing strong color effects (Color Burn, Linear Burn, Overlay) on top of the lineart.

And yes, this doesn't look too underwater-y. A trail of bubbles and "foam" would help since, judging by the way her hair moves and her body is positioned, she just dived into the water so the water should be moving around, not staying completely still.

IMO this is one of your best works, if not THE best. You paid a lot of attention to the headdress, which came out looking absolutely gorgeous, and the type of blurry shading you normally use looks very good on the pearls and skin, since it's supposed to look softer than usual, given the lighting. Love the attention that went into creating the eyes as well, they're the most expressive part of a character for me and I love to see people breathe life into them.

Overall, this looks much, much better than your wallpapers which are based on existing series. I advise you to consider submitting more original works in the future since - judging by this one - the design is of much higher quality.

I feel this looks kind of empty, to be honest. I won't be repeating what HappyTail73 said (for the record, I agree with their comment), but I do want to point out some things I find out of place or poorly done:

1. I'm not normally a fan of product placement but I can let it slide if it's done well. The glasses are well vectored, especially the little Chrome button on the right. However, the typography is...boring. You have the girl, then a pause made up of white space, then the text - which is crammed together perpendicularly. I'm not sure that the Google font really works with anything else, since it's more "playful" than "classy" (which is what the girl is). Furthermore, it's too close to the left side of the screen and too colorful when compared to the rest of the image (strong, primary colors vs. pastel hues).

2. There's too much overall blurring. I don't understand why you blurred her right cheek and the line where the skin meets her hair, on the right; honestly, it looks like I spilled something over my monitor and let it dry without bothering to clean it up. Blurring shadows/highlights is alright as long as you do it sparingly: next time, try combining sharp and blurred shadows (like I did here) - the effect will be great.

3. Some of the lines are wobbly and don't have pointy ends. This makes the lineart look 2D. Also, there are a few spots where the color layer bleeds through, such as the locks of hair on the left and the girl's left cheek.

4. The gradient in the hair is...too simplistic? A few highlights and shadows here and there would've made it look less simple and the lineart for it could've also been a shade of purple/pink, to match.

5. The background is non-existent. Even a few random geometric shapes on low opacity could've done the trick and prevented the emptiness.

I do like the way you did the nails, but I advise you to pay more attention to lineart and composition in the future. Your wallpaper had the potential to be good and eye-catching but, as it is, it seems very rushed and thrown together quickly just to meet a deadline or get it over with. Illustrator isn't a piece of cake to master, but take your time and learn until you can produce something that's technically fit to be submitted (because the lacking technical aspect is what brings this work down, IMO).

I really like the way you combine stocks and renders, it's been a while since I've seen it done successfully. From the larger thumbnail, it looks like a scan or a photo - either way, like the two images were combined to begin with. Love the atmosphere, it's mysterious and somewhat dangerous-looking but also serene and, judging from her expression, almost welcoming. The text is well-placed too: big enough to pay attention to if you like it and small enough to ignore if you don't.

The only gripe I can see some having is concerning the darkness, it'd be good to provide a lighter version in the future as well (I for one don't have a problem with it, but there are some with different monitor settings who may not see all the details). What can I say, great attention to lighting and blending. Good luck in the future, I'll certainly keep an eye out for your works :)

Well, I'll try not to repeat what Cy said, since most of it's what I wanted to say too. I'll just give you a few tips in the form of a list:

1. If you're going with Stroke Path, erase the tips so as to make them look sharp. The way they are now, they make the characters lose realism and emphasize on the 2D a lot. Not to mention the piece doesn't flow as it should when you use round tips.

2. Mercury looks the best and I love Jupiter's hair, but Mars's face stands out - and not in a good way. If the original image lacks detail or the details are too small to make out, use additional images of the characters to help you reconstruct the faces if you can't do it from scratch. There's no shame in that. Also, Mars, Jupiter and Venus lack eyebrows.

3. I love the walls. I have nothing to nitpick about them.

4. The stained glass, however... Let's try it this way: look up images of stained glass windows and you'll notice they don't have very strong colors during the daytime; this happens only when you're inside, the interior is dark and the sunlight is passing through them. Logically, this scene being solely outside, you'd have duller colors. Aside from that, stained glass has texture. I'm not saying you should include big, obvious textures (you shouldn't, since the glass is too far away to see them properly), but they should have something - it won't be visible when you first look at the big picture, but it will be when you start focusing on specific parts of the wallpaper.

5. And two final points about the stained glass: first, try to vary the designs and include more details. Stained glass windows feature lots of details and meaningful scenes (or geometric shapes), and don't usually have empty space. Second, I like that you made it semi-transparent; that's a nice detail.

I would honestly have given this wall a pass if it weren't for the windows. The other things I mentioned aren't that important, but blending colors is a must. The way those windows are now, they look like you made the wall in Photoshop, then switched to MS Paint to color them. Spend more time on your wallpapers, don't rush things and practice a lot before you post something you're not too familiar with (something you're doing for the first time).

Wow, this reminds me of those oldschool celestial and abstract walls, what with the bokeh and the abstract wisps behind her... I'll echo leticiacosmos on the vector part, though, it could use some thicker - and preferably darker - outlines, since she blends into the background too much. I'd first go with making her skin outlines darker, since you can't make out her nose and mouth unless you squint, and the eyelashes contrast too much with the very light skintone (there's no way to balance the black out, since most of the other colors you use are light).

Concerning the background, I'd get rid of the flower brushes on the sides because they create additional focal points (and you only need to focus on the girl, really). Maybe move them behind her, since the wisps are too few to create a "wow" effect. And I'd suggest altering the typography as well: try moving it behind her or even removing it altogether, if it's not something absolutely necessary for the result you were aiming for. For example, the typography on this wallpaper of yours looks much better because it "flows" with everything else; here, it draws too much atention to itself, in detriment of the character.