Torben,
Thanks, these are great issues.
We could put the URL of the resources in the key
then the template could change, but if you change the templates you have to change ALL of them anyway, so you need to globally replace image tags wherever they appear.
I would be open to an api that would do this, I just want it to be easy and simple.
I think we can hold off on an actual implementation until after 5.4 is released and we bring up theming in OpenACS.