So we've done a few adult cakes but never post pictures on our facebook or website because I just think its sort of inappropriate and you never know who will get offended. Anyone have any advice?
I think it depends on what you'd like to do more of. If it's something you're happy to do, and want to cater to that market, go for it. If you're mostly wanting to do kids' birthday parties, or weddings, or whatever, then maybe don't advertise it so much.
Either way, you could put the photos in a section with a warning on your website, so people won't be faced with the photos unless they're prepared.
You can see how I have mine on my site, you have to make 2 clicks to get to them so no one will be surprised. I do not post them on my Facebook but if I wanted to show one off there I'd probably just post a link to the pic on my site.