LAST EDITED ON 03-03-13 AT 00:10 AM (EST)
For the life of me, I cannot see how that could be conclusive that it's a person with a tattoo - it doesn't even look like it might be a shoulder to me. I blew it up to 6 times the original size and tweaked the colour/brightness, and all I could get was that it was a dark object (knee? shoulder? piece of clothing?).
Could be Shamar (dark skin), could be Laura (dark blue pants), could be Julia (dark hair).
Incidentally, Corinne has been doing some dissing of Andrea and Phillip on Twitter since Thursday ... I'm more convinced that she's the boot next episode and there will be two people leaving - a medievac and Corinne.
ETA: Scratch Julia. This looks like her in a vidcap standing with Matt watching Jiffy and the medical team: