Katie Skellington, this wallpaper has characters from both. These four characters meet in Tsubasa and in the xxxHolic manga (not the anime though).

Ah, among the gazillions of what i percieve to be massive, cramed pictures there is one *wallpaper*.

I love every detail of it, my mind basks in Your overwhelming sense of aesthetics (keeps blabbing on about the splendoresque awesomeness of the work)

umm....isn't that Tsubasa not xxxholic but any way i love it