Not to be a creep, but,
When I was with my first guy crush we where in a tent (I know, I know) and he was doing magic tricks shirtless ( I know, I know!). Me, being the casual lurker, crept behind him and started drawing things on his beck. It felt so nice touching his skin and he didn't' even flinch, instead leaned back into it.

Thus, From personal experience, I take drawing on someone's back a big deal.
So you can tell I almost cried when I saw the last gif on your list.

Hurrrrrrrr.
♥ forrreevvahh.