You might also consider Crotons. These shrubs are colorful year round, grow slow, need minimal supplemental irrigation and don't require particularly rich soil. Many prefer bright shade to full sun, many others do well either way but colors may develop differently in shade. Some look even better. I see sunlight on the sidewalk right in front of the bed, so there should be plenty of light for any of them.
Those with really large leaves may try to develop into more robust shrubs, but a once a year trimming would keep even them in line.
Bromeliads have been mentioned a couple times and are a good choice.
Also consider Pleomele, Ti (Cordyline), Spathiphyllum (Peace Lily), Aglaonema and Crossandra.
