Let's talk about self storage.

Does anyone use/have/know where I can purchase the lane dividers that separate parking spaces from each other?  I saw it used one time and it looked as if they used a nail with a colored broom bristle tied to the nail, then the nail was hammered into the ground and it divide the parking lanes....?

If you're thinking of something you may have seen in a self storage magazine it was likely TrueGridPaver.  The company has been around for a while and what you described so well, made me think of them.  

One solution that has been successful for us, is to paint dividing lines on the edge of the concrete and then also paint a number between the dividers.  Our parking area is well compacted grass off the driveway.  I didn't want to bother with reflective sticks and have them getting run over.  We tell the customers, You're space #100 or whatever the number is and ask everyone to be courteous to stay in their parking spot boundary.  It's worked pretty well.  I think our spaces were about 2' wider than a common trailer to give wiggle room.