Hi Toni!
Our garden is in a public park. The wall around it is 42" high on one side with a planter at about 30" on the other side. We've found that the wall gives a feeling of separation from the park but you can still see all around. And noone can hide inside. It makes people feel more secure. There are pictures of our site on our website. Take the forum off the webaddress and you'll get to it.
There are a couple of gardens with a tall wall as a backdrop with engravings. Look at
http://www.theangeltales.com for some pictures.
We put bricks engraved with lost children on the path to the angel. The donors who want their name rather than a child go on the outside of the wall.