I would've thought so, too, unless it was one of those fic icons that look obviously cut down from a manga page or taken from a anime screenshot, but apparently others have been big enough dicks about swipe now and credit later that people now assume that if it isn't credited in the A/N, it's stolen. I always remember to add 'thumbnail=me' on my serial fics; no idea why it slipped my mind this time, but damned if someone didn't use a crossbow to make their point when poking me with a stick would've done the job.