1. That's a texture hashing glitch-- I can't remember the solution, though. Restart the game.
2. There is supposed to be music! You can download it just by playing the map on a server that has the correct files, if you have downloads enabled (which you should).
3. It's possible with a model and .ent file, but that's way much more trouble than it's worth. And anyway, only people with the model and playing on a server with the .ent would see it. So, no.