Yes, but that shouldn't bar you from exploring new ideas. It certainly hasn't stopped Moore (see also: Promethea). The fact of the matter is, dressing up your primary characters in outfits meant to reflect a world in which the Confederacy or the Nazis won is worth nothing more than a BACKGROUND art shot. The story itself had better contain an idea more interesting and original than, "Gee, maybe it's a bad idea to fuck with major events in the past."