I think you and I may have different ideas of what constitutes prehistoric rock art. As you know I am no expert, mearly an informed amateur but I would welcome an open minded discussion at the rocks themselves.
I'd be happy to look at your photos but for a more 'expert' opinion why don't you send them to the rock art professionals at Durham Uni. I have found them to be very approachable. If they consider them to be the real-deal then I'm sure they'll be more than happy to formalise your finds.