It's too simple.

It looks more like a wallpaper for fans than a wallpaper as a "piece of art". If it's to be thought of as just a quick simple fan art, then this is pretty good. But if you're reaching for more, there is so much missing.

A scenery, more detail, a message, a mood, hidden meaning. You have talent. But these things are missing. The featured walls all have a combination, if not all, of these.

I don't think there is much you can do with this scan, so I think you did the best possible while conserving the scan's feeling. Next time though, I suggest you get a more detailed and complicated scan. A challenge, and if you manage to pull it off, a likely masterpiece.

Tell me what you think. :)

Love the simplicity of this one. ^^

This is simple but so beautiful.
Very great work~Thank you!