The way I look at it - if there is a badge available, in the archive, for a ship Name, then I use the original badge whether it be a WW1, WW2, or post war badge. The idea of a badge on an AU drawing is to give it a touch of realism. If there is no badge in the archive then you are free to make up your own. Which you can do in two ways - go to the Empire Badge site (
http://empiretocommonwealth.webs.com/navalships6.htm ) which has most of the badges, from which you can draw the real badge and use it on your drawing (not forgetting to get the KWV seal of approval). Or you can do as I do for some AU ships and design your own to suit the ships name. When making up a badge if you use another artists work, as you would with any other Shipbucket drawing, then you would give credit in the normal fashion.