Hmmm I think I have a Conan pic signed by Arnold somewhere in my hard drive, found in internet... I don't think an Arnold one would be too hard to find as long as you don't need a Conan pic. The rest of the cast would be more difficult... Good luck anyway.
PS: i am sure there are tons of freaks who collect autographs and scan them in their pages, a google search will help. Sure they have a list of the stars in their collections and so, maybe you can go finding some here and some there.