I'm so sorry this happened to you. This is one of the hardest things to work thru.
Personally, I don't know if I'd be able to forgive or not. Like you, I'd keep seeing that image in my mind. It would keep haunting me, and I'm not sure I'd be able to get rid of it.
Naturally you've heard the saying, "once a cheater, always a cheater." I believe in that. However, with your bf, having him come over almost immediately and confess -- I'm not sure that applies to him. Most guys do every thing they can to keep their gf from finding out, including lying thru their teeth. So depending on his actions NOW, and how badly he wants to work on this relationship, you're going to have to make the final decision as to whether to forgive him or get rid of him. I don't know what to tell you about getting rid of the image tho. That's a really HARD one. Just try to replace it with something else I guess.
I wish you the very best. Please take good care of yourself and God bless. Hugs, Lee