Here's my clamp storage. I don't have room on any walls for the usual clamp racks. I do have room in a cabinet above my workbench. I'm tall enough to reach them.
These were hanging on the contraption you see at the right (square board with clamps hanging free), but they would fall on me whenever I went to grab one. This is dangerous, so I redid them with the racks on the left.
I needed to leave room to grab the clamps in the back of the rack, so there's lots of space between the racks. I bolted them into the studs (with bolts I had on hand-overkill, but it saved me a trip to the store) and used Strong-tie "L" brackets to hold the clamp supports. I dadoed them with 1/4" wide slots for all the clamps.
This is how I store the smaller ones. I use an aluminum "L" channel bolted to the door. The clamps are clamped to it.
I arranged the racks so I still had room in the cupboard to store stuff and get all the stuff on the left out.
I could have made the brackets longer to hold more clamps, but I needed room for the ones on the inside of the door. I can add to the middle row if I get more clamps.
I used scrap plywood and hardware I had on hand.
I hope this provides some reference/ideas for anyone else!