There has been an ongoing problem with spam accounts, which the admins have generally managed to delete promptly. This is the first I've heard of such offensive user pictures; I can say that they are not a problem in general, but rather a disturbing turn in the long struggle to keep spam accounts out of the system.

Hopefully the web admin will be able to implement some new anti-spam measures.

it's been particularly bad lately - I don't see the pictures because I'm rarely on the homepage, but it feels like we've had at least one spam account posting here every day - today it's been 4 or so? Admins are fast - I've rarely seen anything up for more than 30 mins - Mr. 555 has been removed already, for example.
There are also "Report Abuse" links on every profile page.
Please do use them when you see something - it doesn't need to be offensive. Anything that's clearly a spam account should be reported, even if it's just spam for cheap software.

Given how little they actually post - it's usually max 4 posts - I wonder if those are human spammers? In that case manually deleting and banning is the only remedy there is. Any word-based filters are a) useless as they're easy to circumvent and b) may annoy regular users who study something with spam-type words (e.g. weight loss) in it.

Spammers do normal working hours, I guess. I only rarely see the stuff, but my viewing hours are mostly in the evening US time.

An off-the-shelf anti-idiot solution is probably best, but I'll pile on after ajlyon and suggest a disambiguation puzzle ...