You really are not going to easily find a photo of cabin X on Y ship. You may come across a review where someone just happened to be in the same cabin you booked. But this is really a waste of time anyway since virtually all cabins in a category are identical. Actually the cabins in several categories may be identical since the category really only defines which deck they are on. Cabins on modern cruise ships are prefabricated units that are lowered into place by crane and welded into the structure.
Which cabin and which ship are you going on?