Any Phlox subulata or douglassii. they come in shades of blue, white red and pink. Choose by colour as there are more names than there are different colours!.
Any Silene except perhaps S. maritima (find that very invasive)
Armeria juniperifolia (or something like that ) white and pink.
Creeping forms of Penstemon (make sure they are creepers, some grow tall, though not as tall as border ones obviously)
Arenaria montana( pink or white)
For yellow go for a prostrate Genista, like procumbens.
Any dwarf bulbs are good.
Dianthus.
Primula auricula types
Crepis incana.
Saxifraga oppositifolia
Any Saxifrage with encrusted leaves, like cotyledon. (Look up section Ligulate for a list of them)
Androsace sempervivoides.
Gentiana verna if liimy. Gentiana septemfida types if acid.
Hundreds more if you want them!
