There will be a reluctance to give you these because of the gruesome nature of the content and also because they cost quite a bit to copy.
There are various areas of possible photographs.
1. The police scene of crime photographs. There should be a list of these in the statement given by the police photographer that lies in the trial bundle. If there is no such report in a case where there should have been photographs, this is very suspicious.
2. Police scene of crime video. This is less common than stills, but the police like to take such videos and so you should ask for a copy.
3. The post-mortem photographs. These are usually taken by the police photographer, but because they are taken on a different day to the scene of crime photographs, they are sometimes filed separately. You need these, even though they show gruesome stuff.
4. Any other photographs taken by anyone which were used in any way at the trial.