The element of 'tropical plants' can be included into most gardens by the addition of lush foliage specimens. These plants may be native to your country, or may not. There is no rule that tropical plants must be 'exotic' as the word 'exotic' can refer to a feature of the plant that is unusual (ie large deep green leaves as comparied to small fine leaves) or can refer to plants from another country.
Tropical plants are typically characterised by coming from the warm humid climates of the world. They tend to have lush foliage and appreciate warmth, humidity but dislike cold and dry air. However it is important to note that the tropics also include desert-like environments and cool mountainous regions so there are indeed many variations.
For more guidance in selecting plants, look at other article on PLANT ID (www.plant.id.au) or in subTropical Gardening magazine - www.stgmagazine.com.au