I think I need to start working on making things a bit more aesthetically pleasing, rather than the underlying code.
I've also largely gotten the rendering code switched over to OpenGL, so I'll start doing some more interesting things - probably make the walls 3D objects first.
On an unrelated note I bought Quake 2 a few days ago and am a bit surprised to be enjoying it. I loved the old FPS games, Wolfenstein 3d, Doom, Duke Nukem 3d - but lost interest in the genre shortly after playing Quake 1. Then again, there aren't very many commercial quality games currently available for linux, so that might be making me like it a bit more.