[mhd]

Done a while ago: https://en.wikipedia.org/wiki/Scwm

There was also "GWM", based on its own lisp dialect, "WOOL", which was around from at least the early 90s.

On the more popular side, you had sawfish (using an elisp-alike, IIRC) and stumpwm (Common Lisp).

[anthk]

Sawfish (the oficial VM of Gnome for a while) had Lisp plugins (or was it written in Lisp too?)