Adding an Icon to a Multicombo

I’m trying to add an icon to a multicombo (not to the multicombo’s options but to the box containing the selected options). I noticed that unlike for text elements there’s no icon property for multicombo elements and I’m not sure how to go about adding a span element via the multicombo’s template method without erasing the multicombo’s HTML altogether. Anyone have any suggestions for how to go about achieving this?