Take a look at Ajuga (carpet bugle). There are several varieties and seem to do well almost anywhere.

Kathy

I just planted Mentha Requienii around some stepping stones - a very low growing mint that doesn't seem too invasive. Its maybe a half inch tall and has leaves even smaller than Baby's Tears. Has lavender flowers in summer. The root system is not much bigger than the plant above ground so it pulls up easily. But I like Ajuga very much - what a trouble free plant. The bronze and purple leaved varieties really set off the colors of the plants above them. Other people I know grow various thymes and they are beautiful. I also like some of the smaller sedums but they aren't going to take foot traffic.

I use moss. Spreads nicely and sets off stone color and texture.

I used astilbe little sprite..also irish moss and woods violets