I made what is essentially a gun rack. It holds 5 machines and has a base for batteries, pinpointers, etc.. The rack is wall-mounted. The metal detectors are stored horizontally. On the inside of the outer boards (on the rack) I use velcro patches to hold the headphones (the container - which holds the headphones) for my ORX and the Deus. Headphones for my other machines are simply hanging on the rod of the machine that the headphones are used with. I mounted the "arms" (that hold the metal detector horizontally) far enough away from the wall, so there is clearance for the coils (attached to the metal detector). Spare coils are kept on another shelf that I built. Beneath the rack, sitting on the floor, are my ORX, Deus, and Vista X. They are next to the wall and completely out of the way, with the machines in their most compact position.
I used cheap fence boards from Lowes. I sanded them smooth, ripped them down to the size desired, and glued/screwed everything together. Then I stained them and put on a couple coats of finish. I've had the metal detector rack for a number of years now - it has held up extremely well.
I don't have pictures, but hopefully I explained it well enough that you get the general idea.