They have thousands of pictures and wallpaper, Touhou oder not! Just type a name in the Suchen bar for a certain character and you'll most likely get 20 pages of Hintergrund and all that good stuff!
Now, I went a little overboard and spent quite a few hours on that site, but trust me, a dedicated Fan would Liebe it.
The site also includes another beliebt Japanese company, Vocaloid, so don't forget to check that out, too!