phossil

Interesting wallpaper... My only suggestion is although you used some fractal brushes, i dont think you should use it on her hair.. (it seems weird). I also can notice some squares in the background, I mean the background isnt all smooth in one piece (distorting lines), it looks like there are boxes of pictures all toghether... I hope it helps. Phossil.

Astrologica

I'm going to point all the parts of the vector I don't like.



I'm sorry to say it, but it looks like your vector needs more work. I strongly suggest you use shapes instead of strokes, for example, on his hair. It's not that shapes are oh-so-superior, but it certainly helps at some parts when you need pointy ends. Then again, if you're using illustrator, there's an option to fix this more quickly, and that would mean yayness for you.
Also, I pointed that some lines look a bit "broken" I don't know how this happened, the only solution I can think of is to make that line again.
Also, don't be afraid of having a line over the other, that's what layers are for, make each line on a different layer so you can delete the excess afterwards (at least that's what I do). Like when his hair meets his chin, it just doesn't look good, for example.

As for the background, I think I'll wait to see if you make a better vector first, good luck =D