plant something small and trailing in it----like moss rose or succulents--will look awesome!

Gardengal, I have similar questions about a rock wall we just built. We don't have a lot of problems with dirt running out yet, partly becuase the rains haven't come yet (that is, they hadn't until today) and I think because my husband quite solidly compacted the soil behind each course of rock before putting the next one on. My back-up strategy is to put plants with fairly fibrous root systems near the biggest gaps and hope that they will catch and hold any remaining debris over time. The book we used for guidance did say that the gaps would eventually stopper themselves with bits of stuff.

Geo-textile behind the wall will do it but if the wall is already built it is too late for that. Buy a large bag of the kind of moss used for hanging baskets and push that into the gaps.

I suggest laying in weed barrier fabric behind the stones and then backfill. An alternative would be to backfill with pea gravel.

I just finished one this summer that is about 2 feet tall. As I backfilled, I wet down the soil about every six inches. I have seen no seepage from any gaps. I did plant a few plants in some gaps but not to stop soil loss. With your shorter wall, you shouldn't have any problems.

The soil should stop moving in time unless it is very fine. Best suggestion has already been made about planting small plants between stones in face of wall. Alternatively, carefully push or hammer in smaller stone between the larger stones. I sometimes leave gaps in dry stone walls so that people can plant alpines but I live in Scotland so the choice of plant is yours to suit your area.