UPDATE #1 :D The ones with grey backgrounds, are transparent, so you can see the waves of PSVITA default setup.
I Found a website that offers lots of wallpapers for the PSVITA, here is the link . You need to click in "show spoiler" to see the actual pic. Here are some that I think are the coolest.
Here is another website link. There are TONS of pics that you people can use :D