One of the tools we're looking to use Zabbix to replace is Weathermap, which produces some nice pop-up graphs on its map-equivalents. In order to keep that functionality, I implemented a quick and dirty method of linking graphs to nodes in a map (Currently only works for host nodes). All it does is parse URL fields looking like "GRAPH: something" and display the first graph matching "something" on the relevant host.
This is good enough for our use, but I expect you'd want to think about the 'right' way to implement this functionality if you included it in a subsequent release.
Screenshot (with obligatory typo, damnit) at http://granite.earth.gkhs.net/~ccooke/zabbix-popup-graph-1.png