The phrase "photo sesh" is a shorter way of saying "photo session." It refers to a planned time when people gather to take photographs. Full definition
haha Just the other day my friend & I were bored in Walmart and went around having a mini photo sesh with various items in various parts of the store haha (glitterinc.com)
Nearly every newborn photo sesh features one of these classic poses. (babygaga.com)