I can visualize your prayer garden and it sounds lovely. The rock idea is great as the whole garden does. I'm sure you miss it
I have what I call is my "love" garden and I certainly pray there and have wonderful thoughts. The garden has been with me for decades, I have moved it several times. Every plant in it came from special family members and friends. I have special lawn ornaments given and/or made by friends
I am in the process of moving it one last time but when it is all moved to the new place, I promise to post pix