Not comprehensive and in no particular order:
i would expect most eateries will not let you bring in stuff from another eatery.
There is an overflow ballroom where they stream the masquerade; it's a lot more fun than being there live, since you can heckle and misbehave a bit.

and i believe there is a place to photograph the masquerade participants; wait for Vay to weigh in, she was in it one year.
I always watch the parade from the step off block; i can get on the shady side of the street and the crowds usually aren't too bad there. Mostly parents with kids. Last year they taped the parade, but i forget when/if they broadcast it.
No DCTV in non host hotels, sorry.

As for stashing a bag at a bell desk-- that's a good question. People actually staying in the hotels do it all the time; outside of DC i have stashed things at hotels i wasn't staying at on business trips. I don't know if there are any public lockers nearby.
As for shipping: the hilton, at least, has a full service fedex office in it. I think the marriott does too. They are very very used to boxing and shipping all sorts of weird things.
