janerowena you should just be able to go to 'Photos' under My Gransnet, click edit next to the picture you want to delete, and two buttons will appear underneath it, one of them being the delete one.
I've just deleted a picture with no problems, BUT I only had one uploaded. It sounds as though for some of you the button has disappeared and for others, it's being covered by other pictures, multiple of the same picture are being uploaded and others disappearing. I'll pass this on to tech and get them to fix the problem.