I have cut pallet rack uprights down to make a workbench. Just cut out the diagonal bracing, cut them to the height you want, and weld the bracing back in. My welding *****, so Im sure they are not as strong as they were, but it works for my purpose.
They make great work benches. I used 3/4 plywood for the base, then covered that with oak plywood and some polyurethane. Completely solid and nice workspace. The lower cross beams are still completely adjustable. I choose to have a lower section for the drill press and grinder, but can easily change that too. This section pictured is 30 feet.
I have another section that is about 40 feet. Some of these uprights are 9 ft (under the loft) and some are 15 feet. I also have one section that I cut the flange off the crossbeam, shortened the crossbeam, and welded the flange back on. I had to do this so the pallet rack uprights would span a man door.
I couldn't do orange and green, so I painted them red.
Its really up to your imagination. You can modify pallet rack systems to fit your needs and they are better and stronger than what you can buy at a box store.