Alright. While I'm not really much of an artist or a waller, I'll do my best to offer as much assistance as
possible.
For the first wallpaper, I think you've got a really good idea behind it. I love the vibrant choice of colors and I
think it's got some major potential there. However, while the character themselves are rather small, it looks like
the scan quality of the image itself isn't that good. A recommendation I would offer in situations like this would
be vectoring. Something like this does take work to learn and practice makes perfect, but there is an application out
there called Inkspace that I know a few individuals use to vector with. Inkspace itself is free, so you don't have
to worry about shelling out any money for it. I'm also not too sure about the background color as well. While, once
again, I like the concept design behind it, I just think it's a bit of a contrast to the vibrant colors that both
the rainbow-styled prism and umbrellas have.
As for the second wallpaper, the characters are definitely a better quality and I like the idea of the cherry tree with
the blossoms as well. A good recommendation I can offer is perhaps a bit more highly quality of the tree itself. It
looks incredibly blurred compared to everything else. Also, the right side of the wallpaper is rather empty as well. You
wouldn't have to make it scenic, but as of right now it does feel rather bare.
While I know this may not be much advice, I certainly hope that I was able to help. If you've got any other
questions, I'll do my best to help.