It depends on the dive.
If I am diving dry, I don't use a pocket on my BP/W at all, I use my drysuit pockets, which are more streamlined.
OK, here's how I configure.
Open Water Ocean, Wet: backup bottom timer, fold up snorkel (as needed). I wrist mount all my instruments, my backup light is attached to my harness webbing, and my SBM is clipped securely between my backplate and pocket so it is streamlined. The SMB is the DAN model that has it's own storage area for whistle, mirror, etc. I have a DIR style sawed off steak knife on my belt.
Open Water Quarry, Wet: absolutely nothing. I don't bother with any backup masks or bottom timer. I am not going that deep in a quarry wet.
Open Water Quarry, Dry: I don't have a pocket on my BP/W (I take it off the rig entirely) but I in my drysuit pockets I carry a backup mask in one pocket, and bottom timer in the other.
Overhead Environment, wet: second backup light, spare mask, second bottom timer.
Overhead Environment, dry: never done it but if I do, I will use my drysuit pockets and carry a spare mask, backup bottom timer, extra light and an extra jump reel.