This challenge is simple. Just make a wallpaper of any anime / manga / video game that doesn't have it's own category on here yet.
I figured this site needs some more of the not-so-popular anime on here, you know what I mean?
There's not really any rules to follow.
I would prefer you use widescreen, but it doesn't affect anything, so don't worry about it.
It will be judged by creativity, quality, and visible effort. The rest you can just go crazy with!
As a side note: I don't like text on wallpapers if it doesn't fit in REALLY well.