[ Stupidity Defined ]
The K one is my favorite! If I was someone who'd just stumbled onto the site, I'd definitely join if it featured art like that. The directional ones with get gold, avatars, homes, etc just aren't as appealing. D:
The second's E one, once again because of the art.
This is basically my opinion, as well.
That and "K" shows Gaia as a 'real place' where our avatars live. It looks like the real 'world' that we're trying to jump into using our avatars. Something like that draws me in much more than something that shows Gaia as "Here's a cool site. Dress your avatar up. Talk". It actually gives you the illusion of Gaia being this different world instead of just a website.