Because some of the Australian state badges were originally created to represent the Governor (as distinct from the Colony) they generally showed some element of British royal heraldry - the main criteria being that it be different from similar badges used in other parts of the Empire.
Queensland uses a blue Maltese Cross (Malta used a red cross). The Crown [superimposed on the cross] on the Queensland badge represented the status of the Governor as representative of Queen Victoria in the Colony.
Ralph Kellyextracted from:
http://www.crwflags.com/fotw/flags/au-ql.html

