Picture Taking -Detente

Yes, when Steven took pictures of John, it lightened the mood between them, making it more plausible that John would have been comfortable with seeing Steven in the restroom and saying "How's tricks?"
But no, I don't think that that reduction of tension would have made it any easier for John to relax before approaching Steven's home the night of the ball. John still wanted to think of himself as straight when he went to the ball. He brought Christina to the ball largely for that reason - to continue trying to convince himself that he's straight.
I often find myself wondering what was going on through John's mind while he was staring at Steven during the song "You Are So Beautiful." Like, he was probably thinking to himself "Why is Steven dancing with that girl, given that he's known he's gay since he was eleven? Why would he want to dance with her? But then, he's doing the same thing I am, right? Trying to look normal?"
I think it did take a combination of booze and the thoughts going through his mind while staring at Steven at the ball for John to get up the nerve to follow Steven home from the ball. John is SO ashamed of his homosexual feelings, that it would not have been likely for him to get up the nerve to approach Steven merely after posing for some pictures, or a greeting of "How's tricks?" in the restroom. (Remember how John looked so panicky when Steven joked "We must stop meeting like this.")