Zivity founder Cyan Banister (that’s not her in the photo, that’s Zivity model Vivka) based her startup on a simple premise: Some women really like to pose for the camera in varying states of undress. Banister’s unique skill is in keeping the site classy.

After launching in 2007, though, Banister wasn’t making her projected traffic goals, and investors weren’t keen on keeping the site’s home-growney vibe. So Banister and her investors — BlueRun Ventures and Founders Fund — spun off Top Fans last year, and Banister and her husband Scott took over ownership of Zivity.

For the past few weeks, Zivity has been testing a new plan to generate revenue and build buzz through sponsored photosets. Here’s how it works: Sponsors choose a topic for which they’d like a photoset and list the prize money they’ll award to the submitted set that gets the most votes from members, who pay for votes. The photo above was submitted in response to a request for “hot girls with camera gear.” Sponsors can specify the amount of nudity in the set, which can be “none.” Oh, but why are we surfing Zivity in the first place?

Banister explained in an email where the money comes from and where it goes:

“We receive 30% of every prize and 20% of every vote that comes in on an entry of a prize. 70% goes to the photographer of the prize. Votes are split 60/20/20 – model/photog/zivity. So, if a prize is 500.00 – we get $150.00. If it gets 2000 votes (which is likely at that prize amount) we get $400.00. So, that’s 550.00 per prize + all of the built in distribution with each broadcast of an entry. All participants share on Twitter, Facebook, Myspace, etc.”

Sponsors so far include flash drive designer Mimoco, Cigar Reader blog, adult site Videobox.com, and Urban Moto magazine (that’s Moto for motorcycle, not Motorola.) The contests’ value to Zivity is that they bring in votes and subscriptions, which is where Banister says most of Zivity’s revenue comes from. “Prizes help with distribution in a major way,” she said.

Looking at the dollar values on the prize page, though, I can’t help thinking the best of these photos are worth more than the few hundred bucks being offered. Maybe Zivity can bring in a rainmaker who’ll boost prize money from the sub-$500 range into the thousands. How about a Zivity/Gizmodo partnership? I’d click on that, and I wouldn’t be alone.