I agree with the corners only idea. Colors can work, too, but if you have more that a few different colors, it can get confusing as well as look messy. If individual truck/furniture location is creating the problem, it is also possible to track everything using wing entrances (1, 2, 3, 4) and number line locations (C, SR 2, SR 4, SL 6, etc.). This is a good tactic if actors are moving things or if the piece has an irregular shape (and can allow for director/designer adjustment without too much tape moving). That's what I did for a show I just closed because it's design was minimalistic and fragmented, so there was a lot of individual furniture pieces and pallets.
Any combination of these or other possibilities could work. You will likely have to make a decision based on what is best for you, the show, and the company.