Thanks for starting this thread. I have been meaning to do it myself (I swear!).
One thing I want to add to what's already been said is that a lot of people come here to check out the hotties in the gallery. No surprise there. But when you send random PMs coming on to them (especially, um, freakishly sexual ones), you may actually contribute to that person wanting to take down their pics and/or leave the site. It's happened several times before.
There is already a place for any of us to make comments on pics in the gallery. Personally I think it's best to avoid PMing people who don't know you, but if you must

- try being respectful and seeing if they're up for a conversation or chat. If you don't hear back from them, the answer is no(hello!). And to the LURKERS - From my perspective, you have a better chance of being able to talk with someone if
you yourself post on the board and make yourself known. Just because someone shares pictures doesn't mean they're up for getting down & dirty, especially with a random person they've never heard of.
Please - DON'T PESTER PEOPLE with PMs. If people take pics out of the gallery, you're spoiling it for yourself and the rest of us.
If the Moderators get too many complaints about someone, we may have to take action.