Where's the photoshoot going to be?
If the pictures are being taken inside and there's no need for additional clothing, I wouldn't worry too much; the photo, assuming it won't be manipulated, will look more natural if you're dressing for the environment and temperature. If you're all layered up it'll look contrived!
What sort of music does your band play, and what's your normal 'look' that you're comfortable in? Don't feel like you should dress unlike you usually do - maybe just neaten yourself up a bit or pay more attention to detail. Add a tie or some badges to the shirt, maybe?
Alternatively you could always wear a casual blazer, military or jersey badge. They're a bit preppy though,

so again it'll depend on your look and the overall feel of your band. A hoody over the top of the shirt with the collar left peeking out or half upturned?
Or you can wear a t-shirt underneath the shirt! If you buy a t-shirt with a logo, brand, or slogan on it that you like, you can wear the shirt over the top unbuttoned.