Here are some UI changes that can be implemented (other beta testers: feel free to post your UI changes here). These are NOT bugs themselves, but rather nice things to have:
May 26, 2012:
1. Add an 'Upload Art' button in the 'My Art Library' dialog, so we can have a quick way to upload without having to open a local folder to drag and drop, etc.
2. It would be convenient to drag art from the 'My Art Library' dialog into the viewport (map area).
3. A button to minimize (collapse) the dialogs would be cool. Since I saw that you are using JQuery UI, there is a short extension for that: <a href="http://www.droptoframe.com/?p=35" rel="nofollow">http://www.droptoframe.com/?p=35</a>
4. A 'bold' setting for text would do wonders when legibility is low.
5. If possible, extend the 'content' area of the website (I'm talking about pages outside the VTT) so that the footer always rest on the bottom of the screen. I will attach a screenshot to show what I mean.
(Btw, this screenshot is from my old Windows partition... I'm using the latest Firefox in my Linux partition).