I think it may have been an oversight on their behalf. It's not a nice oversight, but I think that there's nothing more to it than that. I wonder if, because you were the go-between negotiating things, that may have had a role to play? Although I'm not sure what because even having just typed that has me confused. If it's just the picture and them not commenting, I wouldn't over think it. Perhaps just ask. You could say in a light hearted way, with a smile, "I noticed you commented on everyone ... and you didn't comment on mine. Guess mine was perfect" And see what they say.