In a slightly different context, I proposed something like this for the launcher: themes.
Accounts could specify a color scheme, a wallpaper, an icon pack, and a sound theme maybe, and apps could request them from the launcher upon start. If an app shows up with the proper theme, we can be sure it’s connecting through the launcher to that specific account. This idea was closely tied to another, that I think we should be able to log in to the launcher with multiple accounts at the same time (e.g. work, personal, i-am-batman, etc), and it would be nice to be able to differentiate between the fragments of my split personality with a glance.