No, the dataurl can be anything.
Instead of using the address you could also set the asset ID within Canvas like this:
image dataurl={asset "asset-387e14bf-1938-423b-84fa-fbaecef7b76e"} mode="contain"
You get the asset ID from the asset library.
If you really would like to show / hide then you need to use CSS (opacity) and change this based on your needs. In the APM example you see that the CSS properties (color) get changed based on the results of the conditionals.