If it's just a bunch of troubled loners in normal clothes who have weird powers and abilities, then that's something I feel like I've already seen to death by now.
J.August Richards unnamed character in the pilot at least is going to start off wearing street clothes. I'd like to think that Marvel knows people want a bit of pizzaz. If Smallville
in it's latter seasons and Arrow
can give us that then I suspect SHIELD
will as well given time.