Beaches obviously. Gold Coast and Sunshine Coast, and Fraser Islands. The Barrier Reef starts near Gladstone and there are tours out to Lady Musgrave Island from the Town of 1770. Near Elliott Heads there is a turtle hatchery at Mon Repos Beach, which is really cool at the laying and hatching seasons. Whales in Hervey Bay (again seasonal).
There is a range of hills that runs behind the beaches. Border Ranges NP, Mt Tamborine, Glasshouse Mountains and Noosa Hinterland that have some beautiful nooks and crannies.