How to change photo for my custom units?

I'm making some custom units, using heroes as the template. Can someone tell me how to change the icon on the left side of the screen? When can I find a list of those icons? Thanks!

change the interface icon in the unit editor. as for a list, just use MPQView with the filter .blp on your war3.mpq file and look at the ones under ReplaceableTextures\ tahts wher the commandbuttons are (filename is usually preceded by a BTN, ie BTNtempW.blp)

Thanks! I can continue my work now. :)