I would want to see a good diachronic display of decorative items, including but not limited to the decals, with lots of examples from every country and every decade, with an emphasis on some of the more interesting periods. This should show both how big factories could afford large runs of expensive decals and headbadges whereas small builders would get similar effects by hand. Definitely include some of those amazing Australian bikes with 100% hand painted graphics. And some continental European bikes with fender emblems. French bikes with crazy chain guards. Chain rings.