[EricH]

With regards to the bumpers, I think that would be acceptable. Final determination would lie with the inspectors at your event, however.

For the pit, the projector would be OK if it was used in such a way that it didn't blind people. (i.e., short-range, aimed at a screen) A TV or laptop would probably be better. But the music...

If it's loud music, you will be asked to turn it down/off; after two warnings, you can bid the music (and possibly your pit power) goodbye. (Administrative Manual 4.15, 10th bullet). The music can (read: will) interfere with your team and other teams hearing the announcements. Also note that the pits are pretty noisy as they are: work, conversation, noise coming from the arena, pit announcements, cheering as teams come back from events, and (hopefully not) yells of "ROBOT!!!!!" as teams move their robots around.