The editor-layer-index is the primary index of all available imagery sources, you can preview coverage at https://osmlab.github.io/editor-layer-index/.
- Bing - most large urban areas are covered by hi-res Bing imagery, and even some surprising outback areas.
- AGRI - medium resolution greyscale imagery, covering large continental sections, but gaps due to cloud cover and tile joining.
- Landsat - low resolution imagery covering the entire continent.
Maps produced by the government expire 50 years after the work was created, regardless of publication date. Copyright on other maps has expired if the author died before Jan 1 1955, or if the author is anonymous, if the work was published before 1 Jan 1955.
However, if the map has been scanned, photographed or re-published then copyright can be re-asserted by the person taking that action over their published copy. Where the map is made available by a library or a website they may impose terms and conditions on use of their resources. However, libraries have responded positively to using historical resources for research of historical names - experience has shown their concerns are limited to reproduction of the maps and images.
-  gives a sample of original Canberra maps.
Historical maps available online at the National Library and State Library of NSW  can be useful for street names
- State Library Database 
NSW historic parish maps are at https://www.nswlrs.com.au/Parish-and-Historical-Maps
Most of the parish maps are dated, however they also have a lot of annotations added after the original date of map creation, so you probably shouldn't use these annotations unless the Parish map was "cancelled" at least 50 years ago.
- Out of copyright maps for Adelaide are available from OSMAustralia.org
Recording the source
The Department of Lands in NSW is recorded as:
User:Aharvey has been using
to identify which specific map was used.