There is no reason why you can not plant in the cracks between paths and in your walls. If you don't have any suitable cracks you could make some planting pockets, such plantings will enhance and soften straight lines. Moist plants that will do well in these crevices will like hot dry conditions. The stonework insulates the roots, keeping temperatures more constant in summer and protecting the from frost in winter.

 Few plants will withstand constant treading on so sight them away from the lines of pedestrian access, particularly the taller growing ones. Plants can be introduced into the planting pockets by sowing seed or planting them while small before the toot system becomes too large. Once the get going they will help prevent invasions of weeds, some plants may self seed while others my have to be reintroduced from time to time. Aromatic plants are particularly useful in these situations as the release their fragrance when brushed against or gently trodden on