There are a wide range of possibilities for a themed garden. The design can be formal or informal. From tropical, indigenous to fantasy garden. Mediterranean, Japanese or Italian garden. And so much more.
Theme Garden - Tropical
Our recommendation for Ground Covers for a Tropical garden would include Chlorophytum comosum (commonly know as hen-and-chickens), Asparagus Ferns and Bromeliads.
To have success with a Tropical garden the climatic conditions in your area need to be warm and humid, also it needs plenty of water and rich soil. Plant choices usually include big leaved and lush plants.
We would recommend the following Shrubs, Coprosma 'Picturata', Ixora, Strelitzia, Acalypha, Cyathea (tree ferns), Codiaeum variagatum, Cycads, Frangipani, Hibiscus, Cordyline terminalus, Canna, Clivia miniata, and Philodendron selloum.
As for Trees, the following would work well. Palms, Leopard tree, Feather-duster tree, and Tabebuia.