I finally finished up and committed the search and sort features for art.gnome.org that I had been slowly working on the past 6 months. The site now has a way to search through all themes and backgrounds by name and/or author. The background and theme listing pages also now have the ability to be sorted by date and name to make browsing for what you want a little easier.
As for future enhancements to art.gnome.org, I'd like to make the focus of the site on system themes or meta themes instead of individual (gtk, metacity, etc) themes as it is now. This will integrate better with GNOME and the theme manager. Please email me with UI ideas/suggestions/mockups. We also need to work out a way to separate gtk2 themes and engines and find a way to list what gtk2 engines each theme on a.g.o requires, if any. Anyone looking to help, please contact me.