I (like Bats) love the opportunity to use the word Doppleganger, but the word implies that the figures look the same as the original which they don't. Decoy works but if others feel strongly about Doppleganger, then I am fine that we have to use our imagination.
My next thought though is that Dopplegangers aren't really something that a GL uses. That's more a thing that Lex would do.