A lot of people use miniature thyme, specifically Thymus serpyllum 'Magic Carpet' to fill between pavers and stepping stones. My sister used this, but it was only successful where there was a real gap or depression between the stones (an inch or more)and regular foot traffic couldn't completely squash it. Kind of has the scent of lemon when stepped on, a bit woolly in appearance. It has pink blooms.
Hortster