Well, I decided to try and work on HL2 again, but instead of making a whole new map using just stock HL2 assets (which would invariably box me in as far as theme goes -- abandoned mining town, destroyed city or Combine citadel) I figured I'd port I Don't Know (
http://www.snarkpit.net/maps.php?map=2933 ) to Source. It started out as a HLDM:S port, but then I wanted to try HL2DM, and here it is. I used the original textures, albeit resizing and sharpening them to make them look high-def, and I plan to add bump mapping and such.
----UPDATE----
Changed the name to DM_Convulsion. The name comes from the fact that it's a synonymn of Quake, which this arena looks a good bit like something out of.