Fyre... to answer your questions:
As to what is "art" or at least what would be allowed. I think that, for a web gallery, we're really talking 2d images... that is to say, jpegs, pngs, gifs. No flash animations, no movies, no writings... I don't think I'd be opposed to someone posting a photo of a sculpture they made, same way I don't have a problem with scans of paintings. But I feel DA took a wrong turn when they started letting poems and such be posted as "art." I myself am a writer, many times more than I am an artist, but I have places I go for writing, and places I go for art. Lack of focus dooms most projects. I started Xepher.net with almost no focus at all, and I've been fighting ever since to narrow it down, as I've done so, it's grown tremendously. If I were to try a project like this art site, I'd try and do it correctly from the start, applying all I've learned about building and running a community here with XN.
I feel that the hosting for actual art would be "invite only" but commenting would be allowed for visitors. Whether or not they have to register a "visitor" account to post remains undecided. Mainly this would be for security concerns, because when you don't make people log in, you very quickly garner lots of spam in your comments. Just ask anyone with an open Moveable Type install about comment spam... it actually took down the whole server here a few months ago, before I put safeties in place for such things. The safeties just protect the server resources though, they don't block the spam.
Also, please realize that when I say "invite only" that doesn't mean a direct invite from me neccessarily, but like the gmail model, users will be able to invite their friends. And while they may, in fact, prevent some talented "outsiders" from joining, there's no rule that they can't make friends with a current member and then get an invite. In a sense, it'd be kinda like applications here. If you hang out in the community and start making friends, then it's really easy to get in. This just takes the impetus away from a formalized application process, and puts it directly in the hands of the community.
I actually have a rather complex social model designed for this, one that I've been thinking through over the years that should allow for all sorts of useful stuff. Specifically, because every member would be invited by another, there is a "hiearchy" of responsibility, but also of relationships. This, in a sense, makes for virtual neighborhoods and such... not that such a concept would be a very visible part of the site. Most viewers wouldn't really notice it even... but behind the scenes it allows for some very interesting methods for quality control, dispute resolution, and general jackass prevention. Part of what's sinking DA and Yerf, is that so much responsiblity is falling onto just a few individuals. I mean, Dingo is on a whole assortment of medications for various mental issues now, and according to Lei's post, one of the DA guys is on medication for web-induced stress as well. They're trying to hold the reins to a horse that's gone wild, and they're snapping because of it. Yes, they could (and I think DA does) just appoint a bunch of "admins" to go around and try and manage things, but then you end up trying to manage all the issues between the various admins. Instead of one wild horse, now you've got a team! If, however, you let the community self-select "admins" to speak for them on issues and to keep others in line, the horses are no longer fighting the rider, but are running free... but still a strong community (a herd?) though.
There's a lot of specifics I need to work out for the social model behind it, and the more I think about it, the more I realize I just might be able to do a general site from the get-go... letting the furry and other sub-communities be part as much (or as little) as they want. That would be the real beauty of this social/neighborhood model. At one point I had though about trying to move Xepher.net over to such a model, but I realize that, while some of us really are part of a community here, the majority of sites/users here just do their own thing in their own social circles. Trying to convert this place as it is now to something new would be grossly unfair to most of the people here. A new site though... *ponders* yes, an art site would be the perfect sort of community to use this model in.
For those curious for more details on the social model, I eventually gonna write up a short essay (whitepaper?) on it. For now though, picture it as a blending of absolute democracy, representation, and responsibility. People you invite in are, to some degree, your responsibility. Therefore if someone just sells invites, or brings in a bunch of jackasses, they themselves might be kicked out. Various sub-communities (neighborhoods) will have elected leaders... but those leaders can always be replaced by vote if they're not doing a good job. Anyone will be able to petition for a vote on nearly any issue... from banning a certain member, altering rules, to kicking someone out of office or asking for a changes in features/code. Nearly everything would be run by the community. With any luck, all I'd have to do is keep the server actually running, and maybe make some code changes here and there. I would never have to deal with adding or kicking people, resolving arguments, changing rules, deleting offensive posts, etc.
For anyone that's read "Down and Out in the Magic Kingdom" by Cory Doctorow, you know what Whuffie is... for those who haven't, think of it as karmic currency, or "quantified respect." It's very, very simple. Basically, you give a thumbs up to people you like/respect, and a thumbs down to those you don't. I haven't figured out the exact math... it may be a 1-5 thing or something in the end, but the basics principal is the same. Respect also chains... That is, being respected by someone who is themselves highly respected counts for more than the respect of a bum. Think of it in real life... If Donald Trump calls you a friend, that counts quite a bit compared to the beggar on the street calling you friend. But likewise, for trump... if he hangs out with bums, it's going to hurt is reputation and respect a bit. Not as much as it helps the bum though. In this sense, Whuffie is always being generated. It may hurt your standing a bit to give it to others, but if they're deserving, it's worth more, and once they rise in their status, it will eventually help you to be "friends" with them.
I know a lot of this sounds complicated, but almost all the complication is "optional" or behind the scenes. From the point of view of an actual user, the only real thing they're going to see is the Whuffie scores and the +/- buttons to sort of "rate" people. Just imagine how useful that would be in the average forum though... If you could just "bzzt" a jackass, and so could everyone else. A few stupid posts and by that time tomorrow, the jerk's standing is so low he's not even allowed to post anymore. And yes, I have "safeties" worked in so people can't just team up and abuse such things. Checks and balances throughout.
Okay, this is getting a bit long, so I'm gonna cut it here. Like I said, I'll try and write up a full explanation when I get time, but I am curious to hear your thoughts on what I've presented so far.