yeah, we've realized this is a problem for sites that use secure pages... Someone brought this issue up in a previous meeting, and the best solution we all could come up with was to use a less graphics intense template file (the popup for example): http://ucommdev.unl.edu/webdev/wdngadgetpopup.shtml
And then copy over the graphics to the local site... removing the references to the external 'www.unl.edu' server.
I'm not sure what the best solution is... I know we wouldn't be too excited about distributing all of the template files out to other servers... although we're already doing it with the code, we'd like to utilize the cache as much as possible, and prevent files from getting out of sync. But over https, we may have to look at other options so we can retain browser trust.
This is definitely an issue we need to resolve...
I'm all ears for suggestions.