Tattoos

Going back to the blackwork stuff, I have a tattoo on the top of my left arm that's never gonna fit in with anything else and it's pretty heavy black so I was thinking of getting the area blacked completely but I dunno where to start/stop and what would happen around my armpit.
Dont have pics of the actual tattoo but it's this

And its right at the top of my arm.

Why don't you talk to an artist and see what they would recommend? It sounds like you're not 100% sure on blackwork. Or least go to your elbow.