Just keep in mind that if "Doc" is in the picture and he's a Corpsman, he's U.S. Navy, not USMC... Won't be an issue unless you get detailed with branch tapes, since Doc wears the same MARPAT uniform... Also going to depend on the time-frame.. The first half of OIF, more or less, the Army, Marines, and Navy Docs all wore the same DCUs...
I've modeled the mix of Army and Marines (specifically a Field Hospital during the Marine's handover to the Army at Guadalcanal) before, with the subtle differences in the way Marines/Navy wear the DCU vs the Army... No camo band on the K-pot for Marines, and if their sleeves are rolled up, the Marines roll 'em up "wrong" (inside fabric shows), and for some reason, Marines can never seem to keep their trousers bloused into their boots 5 minutes after they hit the ground... Been that way for decades, from Vella Lavella to Vietnam, and Bougainville to Baghdad...