To be honest, and not to brag, but the first place I'd look for entertainment images would be my personal site, The Infinite Coolness Website™. I have sections about movies, television, music, my own art gallery, and everything else I love. Instead of doing something that's already done elsewhere, I just use great graphics, along with some opinion, and the best links I could find. So, for example I wouldn't make another Buffy the Vampire Slayer site that had the same content as every other one out there, I'd just put up a few choice graphics and link to the best sites. My site is tailored to my specific taste, but if you're looking for the best sites, and the best graphics for a show or movie, check there first.
Obviously, if I'm looking for pictures, I don't have them, so my site is useless for me, but there are some spots that are great places to check out also.
Cinemedia is one of the first places I check when I'm looking for new pictures. It's basically a giant link list of entertainment sites. The place is massive, and while you're looking for one thing, you'll undoubtedly get sidetracked by something else you forgot you loved. It has huge sections for movies, tv, magazines, and tons of other entertainment media. As with any link list, it's only as good as it's submitters, so if you notice an appropriate site missing, or you find a bad link, feel free to let them know. It'll keep the place usefull as an entertainment resource. Be ready to spend hours here, it rocks!
One of the other great resources that I use to find images is Yahoo. Now, I never use their search functions, because I always got stuff that in no way related to what I was searching for, but their index of sites is really excellent. Their TV Show section is great, and I also use their Movie Section a lot. They have a little less than Cinemedia, but the place is still great.
