A couple of years ago, a Scottish artist, Murray Groat (aka Muzki) produced a great series of faux Tintin covers, based on H.P. Lovecraft stories. I just stumbled across these. Given how proprietorial (if that's a word) the Herge folks are, it's not surprising that they cannot be found anymore on Muzki's site, though other resourceful bloggers have posted them.
Needless to say, I find these quite amusing and creative.