Coupled with the headings, use small amounts of text to give a brief description of what the images show. Let me have this text to explain what I'm looking at.
Your gallery pages should be very easy for me to understand. Images on these pages should be related to each other so I don't have to spend time figuring out what the images are trying to say.
If you want to show images which aren’t related, group each set of photos under a unique, descriptive heading with copy that tells me what I’m looking at.