Get some small diameter brass brads, say 2mm or less. You're going use them to mount some cleats
onto the bulkhead. And since they're so small, you'll want a few per cleat.
From there, you can screw or bolt your pictures to the cleats
. You can even use one of a few methods to attach the bolts to the backside of the frames, so that they're not visible, & yet still hold your art firmly to the cleats.
When you go to move or remove the pictures. Detach them from the cleats, & then gently pull the cleats from the bulkheads. And because they were so small, knock on wood, you should be able to steam the holes from the brads out of the bulkheads.
If that doesn't work, or isn't an option, there's always wood putty. And again, given the size of the holes, most folks wont much notice them.