I have no photos, but mine is very simple; it consists of 13 panels, each 10' long and @ 32" high, of around 6-7 bars each. The panels were made by the FFA group at my area high school YEARS ago as sheep panels, and I bought them from them. They are the simplest to use, because I can put the round pen where I need it(right now it is in the center of my large arena), but I will likely dismantle it for the winter, as I won't be starting any driving horses until spring. Of course, it is suitable only for miniature horses!
I believe it is extremely important for a round pen to be LARGE ENOUGH in diameter. Mine is 40', which I consider a near MINIMUM for MINIATURE HORSES. You can do more harm than good, working horses, especially young stock, for any appreciable amount in a round pen that is of TOO SMALL a diameter.
Years ago, when was starting/working 'big' horses with some regularity, I set up a round pen of 50' diameter-the widely-recommended minimum-I quickly realized that that was TOO SMALL IN DIAMETER to be safe and comfortable for my full-sized horses! I now feel that a round pen for 'full-sized' should be at LEAST 60-70' in diameter,at least for regular use.
A round pen can be a useful item, but needs to be used with strong consideration always in mind for the horse's physical well-being.
Margo