Why do we even reinvent (bikeshed) Whonix XFCE branding? 
Can’t we just fork / copy these settings from another project which already figured that out?
Isn’t there a bunch of popular Linux distributions supporting XFCE who figured out decent XFCE theming already?
Popular.  Linux distributions which have good usability and considered beautiful are more likely to be popular, yes?
Using XFCE theming settings which are (mostly) compatible with what’s available from packages.debian.org.
“generic” theming 
Which Linux distributions would be adequate as base to fork / copy over their XFCE themeing to Whonix?
Putting Whonix-Host, Whonix-Gateway, Whonix-Workstation, Kicksecure looking different put aside. This is something which can and should be done on top of this.
 We’re unfortunately not a distribution focused on beauty, usability, fashion. Can’t focus on everything at the same time. This takes time away from other tasks. We reinvent things in inferior ways while we could just take what works from elsewhere.
 https://distrowatch.com probably being the best place to figure that out?
 Obviously we couldn’t use a wallpaper saying “linux mint” (if that was to exist).
Well, it’s always a question of personal preferences, but personnally I like it how it is now with Arc theme and Adwaita icons. I don’t see the benefit of forking existing implementations as of now.
I agree, but what specifically in other XFCE distributions is superior? Take Xubuntu, they also have the whisker menu, some custom icons and custom theme. That’s pretty much all you can do, plus the choice of panel icons/plugins. I think we have it all.
Theme: arc-theme everyone agrees is the best, and now I see it’s installed the Workstation 15 OVA by default. However is it not selected as default theme, this should be the case.
Icons: because arc-icon-theme from github.com isn’t perfect (some icons don’t work well), and because it’s not in debian repo (security), maintaining our own custom forked icons is a great idea. It’s not complicated to maintain our own icons (i.e. monitor to make sure they work, apply minor changes over the years as icon problems occur).
We should also have ksuperkey installed by default. It is currently not.
These basic improvements help Whonix adoption. They should be implemented.
Been using Xfce for 4 years and love it.
Dependencies issue? That’s a bummer. What exactly is the problem?
After an upgrade because of new machine, I’ve been having the issue of Xfce not being able to save settings across reboots, some of the settings are lost even during a simple logoff/login cycle.
For me this is biggest weakness of Xfce at the moment.
I’m not sure about this, I’m not a coder myself, but from what I’ve seen Xfce is being hampered down and interfered with by Systemd. It seems like that to me.
Xfce has to fix this as quickly as possible, otherwise lose it’s king status to competition.
Not off-topic for whole forums.whonix.org but certainly out of scope of this very narrow focused forum thread Fork XFCE Theming of another Debian based Linux distribution. It shouldn’t morph into a general XFCE discussion.