Even on a 27" monitor I like to have my Desktop neat and clean. This has been my basic setup till now.
On the left side, I have the usual list of mounted volumes: my Startup disk, my Time Machine disk and a couple of external drives (technically a JBOD, 2-bay WD MyBook - one for data and one for work).
Just after them, as if they were external drives, two scripts to my Personal Files folder on iCloud and to my Dropbox folder.
The column ends with two remote folders on my NAS server, one for Media and another one for Files.
On the bottom of my screen, I keep three folders for the files that are going in, for the ones that are going out and for the ones (usually images) I'm working on.
As a matter of fact, my personal icons are further customized with a small badge on the upper-left corner indicating if the volume is thunderbolt, usb or connected via the wifi network. The option to add them will be available as soon as I release the source files.