Is this a photo of an MJ-12 meeting?
As it would be hard to find a photo of a meeting for a group that never existed, the answer is no.
However, this photo of a 1948 meeting of the National Security Council does show some alleged members of MJ-12 - Sidney Souers, Roscoe Hillenkoetter, and James Forrestal.
You can find the original at the ARC in the NARA - here.
It's a wonderful resource, with lots of old photos already digitally archived - like this one of Forrestal, looking grim as he walks down the street. Note the guy to his right in the background, filming him.
The ARC site makes history come alive, which is always a good thing. And who knows - maybe there are some UFO-related nuggets hidden in there somewhere, waiting for a diligent researcher?