[Repeated from a similar question last year.]
Everything. Books, television, movies, music, comic books, art, even food. As I answered last year to a similar question, you could say my source is immersion. Whether creating a new character or planning to run a gain, I like to surround myself with sources of inspiration: music, books, movies, images, online sources, etc.. I browse the ‘Net for related materials, I scour my creaking bookshelves, I cook recipes from particular cultures, and so forth.