Oxygen icons package -  5.100.0-1.1 is installed.

The Dolphin folder icons do not properly display the Dropbox badge. Instead of
the proper badge a gray square is displayed where the correct Dropbox badge
should be. 

Tango and other icon themes do properly display the Dropbox badge on the
folders.

To replicate select the oxygen icon theme and open Dolphin with the Dropbox
daemon installed and running.

You will see the small gray square where the proper icon should be.

Select the Tango icon theme. Open Dolphin and you will see the proper icon
badge displayed on the Dropbox folder.