Sorry to say that most here suck.
Googling Mario and Luigi and adding a paint tool background does not make a good wall.
Anyways, here's the two I've used since I got my PSP a few days ago.
I resized the DAFT PUNK one on my computer, normally I just zoom into it on my PSP and add wallpaper.
I actually also use a DOOM wall too, but I use the PSP zoom method and don't want to try resizing from PC.
Oh, I made the CaveStory one myself using images on a fansite.
I had to edit some of the mugshots to make it fit in a quilt-like fashion.
edit: Oh, duh! Take a screenshot of it!
