Heath,
good catch, I missed seeing the barrel with the 3 guys until I opened the photo. Now if we could only see the bottom of the tire. The camera angle/altitude relative to the drums and tire appears to be fairly high, making judging heights difficult. The drum is roughly on the aircraft centerline (the hose appears to touch the nose), making the port landing gear about 6 feet closer to the camera. That should make the port tire appear larger than an equally tall barrel, but to be sure the tire and barrel image dimensions need to be measured from top to bottom, not just comparing the tops. The barrel looks unusually large/tall, relative to the 3 guys. Maybe they're quite short?
Is the tall man standing on the wing, wearing dark clothes, Fred Noonan? Wasn't he about 6 feet tall? A standard 55 gallon barrel is 35 inches tall, or about equal to a tall man's trouser inseam.
The paint on the leading edge is clearly visible in the photo, which might interest some folks over in the artifact thread.