Tropical plants look great around a pool. Look for plants that have big leaves and lots of flowers or colorful foliage. Here are some candidates that come to mind:

Trees:

Big-leaf magnolia
Cucumber magnolia
Sweet-bay magnolia

Shrubs:

Swamp hibiscus (mallow)
Scarlet hibiscus
Confederate rose
Tropical hibiscus (will need to be brought indoors for winter)

Perennials:

Umbrella plant (papyrus)
Canna
Elephant ear (needs heavy winter mulch)
Banana (needs heavy winter mulch)

Annuals:

Coleus (many colors and leaf shapes)
Sweet potato vine
Caladium
Morning glory vine
Cypress vine
Purple hyacinth bean
Moon vine