I generally consider Tropical Bonsai to mean plants that normally like to keep there root zone at or above 50 degrees.  This is very general because many "Tropical "plants can live through freezing temps but will suffer damage to the growth above ground.  Tropical Bonsai are good candidates for nice ceramic bonsai pots because of there is no chance of damage from freezing.  We will try to indicate general growing condition but will be happy to help you with specifics to your growing area.