What should you be putting into your pack when you head up to a tree stand, beyond your gun or bow and ammo, to hunt whitetail deer?
You're making a big safety mistake by putting your gun in your pack when you climb into a tree stand.
In reality, it is safer to haul up all of your gear, including your pack, and your gun unloaded with the action open by a rope, rather than have it on your back where it could a) go off or b) hurt you when you fall. You could also damage the gun.
As for other things to bring, the list is subjective:
You can bring more items, and leave them at the bottom of the tree stand, say in your pack, and use the rope to bring up just what you need. You can always go back down to get something - as it can get awkward sometimes having a lot of equipment in the stand with you.