Spoiler warning! This video shows off most, if not all, costumes in the entire game, including every playable character. If you want them to be kept a surprise, don't watch this video!
I accessed all of these costumes via modding, so I don't know which of these are available, or how they are available (I suspect many of these are available only via re.net). The weapon loadouts you see here are sometimes for a different character, something you can't do without modding.