There are many different ways to display armor. Of course you can just hang it from the wall or a beam. The first image shows (mostly) pieces hung by wire from hooks in beams. Most people don't have beams, but you can do the same thing using hooks in a wall or, like the second image shows, something that acts like a picture moulding. In this case I used a stained 1x4 and then I hung pieces from this using small hooks. The second image also shows a few simple helmet stands.
But it is often interesting to display "suits" or "half suits" as a unit. To do this, you need to have some kind of form that supports the pieces of the armor in the right positions. Here are several different ways that can be done. I am certain that there are many more.