coolnz.net – The final choice seen with World flags
Compare how well the designs stand out among other flags:
As well as Australia's flag, there are a number of island nations that have the same blue with the Union Jack (eg. Pitcairn, Cayman Islands). There are lots of flags similar to others, but the ones that are easiest to recognise (and remember) work well for them because they are different.
Of course, the added designs above and below would be fluid and less-focussed like the others.