I've seen several different clamp storage ideas. This is my version of the upgrade from a 2x4 screwed into the wall. With a relatively small amount of wall space I have stored....
2 4' aluminum bar clamps
3 4' steel pipe clamps
7 bar clamps varying from 2-3 feet
4 wood hand clamps
5 small quick-grip clamps 12 inch
4 small bar clamps 8 to 12 inch
2 strap clamps
several 'C' clamps
And storage to add 4 more bar clamps. I have the 3' pipe, just need to pick up the clamps sometime.
The improvement here is the clamps are housed on cleats that extend from the wall. In 6 inches of wall space I can store several pipe clamps and even more bar clamps.
See a couple other clamp storage ideas that are both more mobile, and show better craftsmanship. In my case I have a stationary space and need to keep as much things on my walls and off the floor as possible. As far as craftsmanship goes... Just use this as an idea and learn from my design errors.
Step 1: Attaching the Cleats to Store the Long Clamps
First picture shows one of the cleats that was screwed onto a 2x4 attached to my wall. This is a chunk of wood ripped to the thickness of my quick grip clamp, then simply glued some thin wood to the sides, and screwed the cleat to the 2x4. This process is repeated many times.
The species of thin wood in this picture looks like some leftover cherry. Most of the wood was some leftover white oak. Used up most of my quarter inch oak that was laying around.
On the high clamp fixture I used some quarter inch white oak and screwed the cleats from the back, then attached the fixture to the studs in my garage. All in all, it is easier to simply screw the cleats to a 2x4.
The fourth picture shows a bit of 'field engineering'. The first set of cleats were parallel to the ground. Put some clamps on the cleats, and one promptly spun, fell, and bonked me on the head. Solved that problem by gluing the ears on the end of the cleat. That doesn't stop the clamp from spinning, but does keep it from falling and bonking me on the head.
The design solution is to cut the strips at about a 20 degree angle so the clamps will wont want to spin. The small clamp cleats are cut with this angle, but doesn't show up on the picture very well
the last picture is some of my long bar clamps being held by the cleat.
Step 2: C-clamps, Strap Clamps
Not much engineering here. To store my collection of c clamps. cut a chunk of 3/4 oak to about 2 inches, cut at about a 20 degree angle and pocket hole screwed to my 2x4. Slide the c clamps on to the scrap wood.
Strap clamps were definitely an after thought. These little gems typically sit on a shelf on my bench, and them handy little corner squares have a nasty habit of falling which requires me to go hunting for them on occasion. To put them on my handy little clamp system I simply screwed a chunk of quarter inch oak to my 2x4 and used that as a brace. Have 2 strap clamps, so added a second brace.
Step 3: Spring Clamps
Here is where I keep my spring clamps. These simply clamp onto my steel rack. These have had a home on this rack for many years. They didn't want to move to join their other clamp friends, since they were happy here, and never fell and bonked me on the head, I decided to keep them on my rack.
There you have it, my solution to storing my various assortment of common woodworking clamps.
A couple suggestions for your own use....
Cut the cleats so they have about a 20 degree angle.
It is easier to screw the cleats to a 2x4 from the front than a thinner piece from the back.