Stock photos of real science is hard, it's easier to put someone standing at the side of the equipment they use in the real scientific work.
For experimental physics I like the photos of optical tables ( https://www.google.com/search?tbm=isch&q=optical+tables+lase... ) and the racks with a lot of electronic equipment ( https://www.google.com/search?tbm=isch&q=physics+laboratory+... skip the first 10 images). They look like something you may find in a real laboratory.
Theoretical physics is harder, they look like normal people (i.e. mathematicians) until they start to talk about the real word. I prefer to discuss writing in paper, but for a photograph the only sensible solution is to write a bunch of slightly related equations in a blackboard.
(And there are many other science branches. For Geology you may put someone with a bunch of rocks, but I don't know a real geologist so it may be not a representative image.)
