You can if you're editing the code of the HTML and CSS, but there's no way to tell InDesign to do that in the HTML and CSS it exports.
Do you think this is something they will change in the future or make a plug-in for? It just seems logical that if multiple pages within an InDesign document can share one piece of art that you should be able to export just that one piece of art and it is still linked in all the same places.
I can't tell you that.
InDesign's EPUB capabilities have improved with each version, and I would expect that that would continue. But only the product managers know what features might be added in a new release.