I think one of the best things you can do to a workbench is to add swivel casters (for moving to where the work is, sweeping up and to find that dropped part)to the legs. As I am not a fan of locking casters, I mounted two "jacks" made out of threaded rod and swivel pads on the front legs to keep it in place.
I added a 3-1/2 foot high plywood panel across the back. Using an assortment of screw hooks and screw eyes, I have a place for every tool (combination and cresent wrenches, screwdrivers, sockets, pliers, vicegrips, hammers, center punches, tweezers, putty knives, utility knife, magnifying glass, etc.) I need for the stuff I usually work on. On the back side of this panel are lesser used tools (larger hammers, air tools, torque wrenches, transfer punches, gasket punches, etc.) My workbench normally sits perpendicular to the wall so both sides are accessable. (Before I built this organizer, I could not believe how much time I wasted searching my tool box for what I needed.)