Well, it's not uncommon to show people pictures of your girlfriend/boyfriend (this happens all the time and most people wouldn't even consider it necessary to 'ask permission'). We weren't asking for nude pictures.
But key factors here are you already told us you slept with her after the first date AND this is a forum OPEN TO THE WORLD. So yeah, taking these two factors into consideration, I guess you should take the advice of the ladies (funny how none of the guys realized this until the women pointed it out) and ask for permission OR just avoid the issue altogether. She may just have a problem with you even asking (especially if you went out of your way to tell her the entire truth - the fact you came on here, asked for advice, then shared your success... btw, as honest as I like to be, I'd advise you NOT to tell her the whole truth, hell, into you're at least 6 months deep.)
But yeah, I don't think you should feel guilty. Cheer up and enjoy the ride. And goddamn, that backpack of Harry Potter/ Obama and Sonic rocks.