What

I believe it would make some sense for Fedora (especially now with new logo and new branding) to actually expand its default theme sound with some Fedora-specific sounds for branding reasons.

Why

Windows and MacOS generally have several sounds for several actions, including sounds for when the system boots, is shutdown, or even during login.

While those sounds might not really seem important, it's part of the identity of the OS and usually the sound becomes quickly and easily associated with the OS (whether as a good sound or bad sound depending on how they thing of the OS).

How

The list of possible sounds for the sound theme are available here: https://0pointer.de/public/sound-naming-spec.html

From this list, the ones that I believe would make the most sense for a Fedora-specific "extension" would be system-bootup, system-ready and system-shutdown.

The libcanberra services that are used to play those sounds currently are shipped as disabled.
those are: canberra-system-bootup.service, canberra-system-shutdown-reboot.service and canberra-system-shutdown.service.

I don't really know whether this actually is something the Fedora project would want to have for branding and also whether it it should be an opt-in or opt-out feature (by managing the canberra services I mentioned before, although this might require a UI on the Settings app to not CLI exclusive).