Depends what you are able to manage.
Swildons entrance series has virtually unlimited photo potential providing you can manage Binnies Link and Jacobs Ladder.
If you are looking for easier than that, then I'd highly recommend a mine or two.
Sandford Levy and Compton Martin Ochre Mine both have lots of fantastic details to photograph as well as mine shaped passages. Intending to take my big camera back to both of these mines soon. Note: Compton Martin Ochre Mine is up a steep slippery slope which may or may not be too much for you at the moment; access Sandford Levy is totally straightforward.
Somebody is bound to say Goatchurch, but in terms of photos it doesn't float my boat...
Mind you, earlier this year someone posted a fantastic photo of Aveline's Hole, so anything's possible!