I'm having a bit of trouble accepting that one of the dialogs that is presented to me as frequently as the XScreenSaver unlock window below is by far the least shiny part of my daily Linux desktop experience.

Tuning just the knobs that XScreenSaver already comes with, I eventually got to this point:

The logo still is too much noise and the font still lacks anti-aliasing. However most of the text noise, the pre-90s aesthetics and the so-called thermometer are gone. To bring it to your desktop, use this content for ~/.Xdefaults

xscreensaver.dateFormat:
xscreensaver.passwd.body.label:
xscreensaver.passwd.heading.label:
xscreensaver.passwd.login.label:
xscreensaver.passwd.thermometer.width:  2
xscreensaver.passwd.uname:              False 
xscreensaver.passwd.unlock.label:

xscreensaver.Dialog.background:         #000000
xscreensaver.Dialog.foreground:         #ffffff
xscreensaver.Dialog.Button.background:  #000000
xscreensaver.Dialog.Button.foreground:  #ffffff
xscreensaver.Dialog.text.background:    #000000
xscreensaver.Dialog.text.foreground:    #ffffff

xscreensaver.Dialog.shadowThickness:    1
xscreensaver.Dialog.topShadowColor:     #000000
xscreensaver.Dialog.bottomShadowColor:  #000000

and run

xrdb < ~/.Xdefaults  && xscreensaver-command -restart

as advised by the XScreenSaver Manual. For other approaches, I'm only aware of this one: xscreensaver lock window themes. Please comment below if you know about other approaches. Thank you! PS: The screensaver in the background is Fireflies. For a Debian package, you can run make deb from a Git clone.