Nice crossover
well, maybe you can blurred the lines a bit? coz it looks like a sticker, if you make the lines like that, or maybe change it into a color that match the background?

This looks really Easter-ish~

The animals are really cute haha. The grass looks really fresh too, and although I don't normally like grass in anime wallpapers, I think it looks pretty nice here. I think the outlines are too black though, making this look like a coloring book. Chii and the animals also look a bit flat compared to the surroundings, especially the swans (they look unfinished since there is no shading on them). The inside of Chii's dress is showing and those parts should be darker than the outside (if you were going for the flat look, the grass is too real looking).

That said, I still really love the nature-loving aspect of this wallpaper! On the whole, it's also really refreshing. I would like it if you wrote that the meaning behind this wallpaper is to warn people to take care of nature, and if not, we will not get to enjoy it much longer like Chii can. But that's me being too much of a moral advocate, hehe...

Your orginal drawing was cute too, haha, and it resembles the Doremi girl who you seem to be obsessed with.

Aw, this is so cute and lovely!! And really really well done!! Wow, you drew those animals! You're so talented! And Chi-chan really does fit in perfectly here! And I love all the effects you did! Amazing job, fave for me ^_^