I had one of those off-the-shelf display racks but after several years of visiting different courses I ran out of room. Rather than purchase another rack I decided that creating my own would make a good project, and I could design it to be extendible.
The technique I used is pretty simple. Anyone acquainted with the most basic tools should be able to handle it. It works with any design that has a solid backing. The world traveler might get ambitious and use it on a wall-sized world map (using raised 1/4" plywood for the continents). You could even apply the technique to a plaqued photo of you beside that hole-in-one flag!
Sadly neither of those apply to me so I opted to mount the balls on the side of a bookshelf that lives in my office. The shelf is rather tall and the space beside it is unoccupied so by mounting the balls on the side I didn't waste any space and I had a lot of room for expansion. The photo shows the final result.