I’m not a Steelers fan, but I did look at Cowboys jerseys and found one that could be my size, but the recommendation is to get one size larger, which doesn’t exist. Thanks, though.
Same here. I’ll wear a t-shirt under it in warmer weather, a long-sleeved t or a turtleneck in colder weather.
Maybe you should email the organizer of the group and ask for the name of the female in the photo.
I don’t think that you’re going to get much of a discussion. Despite assertions to the contrary, “anything you feel like” is the only appropriate answer. There is no etiquette involved here, or “guidelines,” or “standards” of any kind.
Well played.
Does Airman know? 
I prefer a men’s size jersey (ditto my Penguins’ jersey), because I like them nice and big and cozy. And I always wear mine over a long-sleeved shirt. I want to get a new Steelers’ jersey, since Willie Parker doesn’t play for the Steelers anymore. (I want a Troy Polamalu jersey)
Wilbo523, I take it you’re not a sports fan?
I always wear a shirt under my hockey jersey, but that to protect my jersey.
Thanks. Coffee makes a lousy screen cleaner.
It may have come up in casual conversation a time or two. 
I have a couple of pro-styled Broncos jerseys and don’t wear anything under them, despite the tiny holes for ventilation. I don’t really regard it as see-through, and being a guy, don’t really have anything to show (besides man boobs and hair, but I like to delude myself into thinking that my jersey conceals rather than reveals.) And I live in Arizona, where it does get cool in the fall and winter, but rarely freezing in the daytime.