The only thing I can think of is Iberis, which, if pruned severely after bloom, will stay small and tight.

It's not a weird idea at all, but with ground covers, I think you'd have to trim and tend it almost daily. They usually do those with herbs/tiny shrubs/annuals, more upright plants that don't escape their original boundaries in a short time.

Different varieties of Sedums might work. What about Hen and Chicks?
Mike

Have you considered dwarf mondo grass (Ophiopogon japonicus 'Kyoto dwarf' or Ophiopogon japonicus 'Nana'. These plants resemble grass but have darker and wider leaf blades. They do spread so you may need to keep them in check.