We have an irregular bluestone walkway leading to our back door. Spacing between the stones varies from 1.25cm to 3.75cm. Though on the south side of the house, heavy deciduous tree cover shades the area for most of the day, permitting "direct" exposure for about 2hrs in starting mid-morning.
We would love to get something established between the stones, but don't really know what would be good choices. Ideally the plant would be well behaved and not creep out too far over the stones, but that wouldn't be a deal breaker.