There is a time limit to copyrights. If it's a project Gutenberg, it's public domain in the U.S. Do a search on H. G. Wells while you're there. War of the Worlds is public domain too. So is Alice in Wonderland, Peter Pan, and the Wizard of Oz. Make furry footed Munchkins to your heart's content. Call your fairies Tinkerbell. The thing to remember is that 90% of modern copyrights are based on expired (and in Star War's case, unexpired) copyrights by other people. So long as you don't copy exactly, or to the point where a trademark is involved, you can probably get away with it. No worries. The big exceptions are things like Mickey Mouse, Star Wars (although Lucas stole so many ideas from OTHER authors a lot if his stuff wouldn't pass close insepection), and comic book Superheros. Also something to keep in mind is labeling. Specificly calling something in your art the same as something that activly protexts it's copyright can get you in trouble, where if you just keep your mouth shut you're safe. Don't name your pictures "Mickey Mouse Meets Godzilla with Superman watching approvingly" and believe that you're safe. On the other hand, a mouse in clothing fighting giant lizard with a laser knife, while the superhero smiles (avoiding the obvious trademark infringemnts in the picture itself), should be perfectly acceptable.