Also fixed the problem with the slow loading times. The problem wasn't with SharpZipLib, but with Direct3D. Apparently the Texture constructor for streams really sucks, use TextureLoader.FromStream instead(plus FromStream supports Targa images).
One of the levels from OpenArena. I tried implementing light-mapping, but it's really blocky looking.
Now I'm going to try and parse the "Entities" lump so I can implement starting positions instead of wondering around trying to find the level.
Edit: Oh yeah, thanks to Hippo for giving me an invite to Great Games Experiment. I have two invites if anyone wants one, just post your e-mail address here or PM me(don't e-mail me, I'll never see it).