Steps and stones can look good with plants growing in crevices. If you have dry conditions, Erigeron ( below right) is ideal and once established self seeds wildly. In wetter. more shaded condition. the ivy leaves toad flax (image top right) which is a common wild flower will establish itself in crevices and look very attractive.
This is also true of Thymus (image below) which being a mediterranean herb love it dry and stoney. Thyme is a traditional plant for growing in paths.