Did you line the inside with any geo fabric? What's going to keep the soil from washing out between the stones? How tall is that wall- did you slope it in towards your side to help hold against the pressure of the soil??

Are your planting pockets along the top or sides? How much sun will they get? Frequently, alpine or Mediterainian plants that require sharp drainage work well in this type of situation- look into creeping thyme. Or search 'alpine garden' Rock garden plants.

I like moss. If the concret is aged it should take but make sure the moss comes from the same type of situation. If your area is in sun get a moss that grows in sun and If it is shady get moss that grows in shade.
I agree with creatrix for other choices.

that's quite a wall :)

I've got dragon's blood sedum, and a different kind with green leaflets and little yellow flowers, something called RockCress that's kind of like a creeping phlox, only the flowers stand clear of the foliage...thymes, mosses, most succulents, corydalis (mine were volunteers!) though that likes some shades,
if it gets lots of sun, succulents tend to work well, if it gets some shade, even things like lamium, and some of the smaller ferns can be packed in the cracks, depending on how much room there is for the roots.

you might also want to check out the 'alpine' forum, which does a lot of 'rock garden' work :)