What zone are you in?

FataMorgana

Common thyme(don't know if it's the same as creeping thyme)survives the winter in the ground here, with the temps going well below zero. It has even survived being in a large cinder block as long as there is snow cover. HTH

Sorry. Didn't list zone before. I'm in 3/4.

Creeping thyme works here in Ohio.
Common thyme gets very large and might not work between stepping stones.But it is a perennial.
If you buy a couple creeping plants next spring, they can be divided and spaced here and there. It takes patience for them to get going, and some tending to in order to keep small weeds from invading at first. Wooly thyme is also a low grower, but don't know about its zone.
Type in Steppables in your search engine and you would get lots of ideas. This is a company that specializes in these small plants.

Your zone will cut down the choices considerably. The list of zone 3 hardy plants that may do well for steppables is much smaller. Herbaceous herbs like yarrow that could be mowed, if your stepping stones are flat and close to the ground, may be good, hardy choices for your zone as well.

FataMorgana