I agree with Chubbs that too many sub categories could ruin it. Here's my thoughts tho...
Music
Album is obviously already done, but Best Song and Best Band are obvious ones. Perhaps worst as well, as they tend to be just a fun
I think it would be too difficult to pick best songs. You would probably end up with a very split vote too. Plus it can be hard to judge one song you really like against another of a totally different genre. Best bands or male/female solo artists could work I suppose.
Film
Best Film could be broken down into genres or just comedy/serious perhaps. Would best actor or best character be better? as people tend to mean the latter when they vote for the former.
Best actor or best character polls don't appeal to me personally. I'd like to vote in a horror films of the decade poll but I accept that might be not be a widely held interest.
TV
Best TV show again can be split as the films are, best character is a definate here I think, possibly worst show as well so Simon Cowell can win something. Or Bonekickers, that was woeful.
Best character would work better here than in the film category. I think a best TV comedy series would be well worthwhile. Best cartoon series might be good too (altho most of these would prob fit in the best comedy series so maybe not necessary).
Sport
Split this into STFC and non STFC- Best and Worst moments, Best and Worst performer/single performance,
Culture/Other
Best Computer game or something like that?
All these would work. Something to think about is would all these categories be a top 50? For example do we really want a list of 50 worst swindon moments?