When the ex sends you a photo with the new girl. Advice?

So I was talking to this guy for a couple of weeks and he asked me out to a sports game, 2 hours before the game (which I was going to regardless of him asking me out) told me he was going with lanother girl” instead, and he’s “sorry he didn’t tell me sooner”. I spent weeks “talking” to this guy and he just found another girl and asked her out the morning of the sports game before school (what I heard from mutual friends). Anyways, flash forward a couple of days and he’s sending me like sad douchey photos from the gym lifting weights...how considerate. But I never really replied let alone with words (by this point, I just snapped back pictures of my wall or something) because if anyone reading this has snapchat, wall snapbacks aren’t the most personal or I want to talk to you back response. On a different token, tonight I was just hanging out watching Netflix when all of a sudden he sends me a photo of him in bed with the girl from the sports game. He was smiling and she was covering her face under her shirt but it was just awkward. It’s been like 4-5 days since I’ve talked to him and then he just randomly sent that of him and his “new” girl. Some of my friends are telling me to block him, not reply, reply with something petty. I don’t know what to do? Any good advice for anyone who’s been in a situation where your (basically) ex texts you photos of them with a new girl?