Just a quick dump of what anime wallpapers I'm using on the laptop this month. They're all sized to 1400x1050 and generally darkened by about 50% from the original to make for a background that doesn't interfere with the foreground windows. Sometimes, if I'm sizing and image up and it doesn't look okay, I'll apply special effects to the image in Jasc Paint Shop Pro.
Trigun and Bean Bandit (untouched except for resize and darkening)
Tenchi Muyo - Ryo Oki (darkened, with edge enhancement or something)
Priss from Bubblegum Crisis and Trigun (fine oil brush filter effect)