Fun idea, but I can see a potential problem when the time comes to mow. I think the glowing rocks need to be contained somehow. Or maybe use larger painted rocks to line a walkway and just plan to use an edger for trimming the grass.
THIS IS WAY COOL! Recycle, Reuse, Re-purpose! Totally cool reuse idea. Especially if you were to utilize them for growing food! The beautiful decorative tiling is optional. The concept is brilliantly creative use of old rims! Bent or broken, still useful.