Yep, I created a 3D Skybox for HL1
http://www.acidplanet.com/artist.asp?PID=732119&T=208
Sorry, vids only like 2fps, but you'll get the picture..
mind you, this was just a test, and it turned out great.. lighting and such would be fixed if it was being used for other purposes.
So tell me what you think.
(To avoid buffer time/wait, I'd suggest downloading)