Couple of thoughts.  We recently installed an inexpensive track system for hanging stuff from the wall.  It is made by Rubbermaid, purchased at Home Depot.  It consists of a simple metal track that screws to the wall, a plastic cover that snaps onto it, and various types of hangers that clip over the system.  We use one hanger for the manure forks, broom, etc., one for the hose and extension cords, one for folding chairs and the hanging bag with horse balnkets and saddle pads.  And the beauty is, if you need to use the stall for a horse, the hangers are easy to unsnap and all you have is the track flat against the wall, no sharp edges and nothing sticking out.

Also bought a set of those plastic drawers you can get at any home center, sold for garage storage.  They come already assembled, are plastic so nothing will hurt them, are light so the can be easaily removed if you need the space.  Great for all of the small "stuff" you need.  All I did was add a couple of screw eyes to top, bottom, use them to attach a bungee cord to keep drawers in place while trailer is moving.  Piece of cake.  I got a 4 drawer set, about 36"W by 36"H by 12" deep.