After a little fruitless searching, I was unable to find a shelf to display some of the models that I have printed.  Also, one thing I wanted to incorporate into my design was to hide the command strip, which I did. I designed this in about a day.  It took a couple of test prints, and modification but I am satisfied with the results.  

The only real installation instructions are to place the command strips 145 mm (5 23/32") apart measuring from the outside of the strips.  This model uses the Medium 3M Command Strips found on Amazon which is linked.  link

I added a template to help install the shelf, it positions the strips 145 mm apart, which eliminates the need to find a metric ruler, which can be hard in some areas.  It also will help align the shelf with an existing shelf.  The align top indicator, aligns new shelves to the top of existing shelves.  It also has centering indicators, so the only issue is leveling the template before installing the command strips.

UPDATE: This is great for apartments where you can't drill holes.  Or if you don't want to deal with filling holes when changing the shelf locations.  I have also added a new shelf size, which is deeper, but still uses the same size command strips.  It is in the last profile.  The shelves are 7 inches wide, and the one that is brown in color is 4 inches deep, the one that is white is 5 inches deep.  They use the same mounting template.