Annuals: Tend to grow faster. Try Lobelias, Begonias, Dianthus, Impatiens, Coleus.
Perennials: Take longer to grow, but well worth it. Try Roses, Fuchsias, Geraniums, and Succulents all do well. Miniature varieties are especially adaptable.
Herbs: Can be planted in the top once the bottom plant is established. Try Parsley, Chives, Mint, Sage, Coriander, Rosemary, Lavendar, and Aloe Vera.