You can add the following to your fvwm configuration (for example)
Where randomimage.lisp is the name of the executable file you named the
above as. If you are not using clisp, you have to remove the first line in
the program and add the according interpreter call in front of
“randomimage.lisp” in your FVWM configuration.
Using XV to set random background image
From the ancient times XV has been
used for this purpose in the following way
Using wmsetbg to set random background image
wmsetbg has better support for pseudo transparency than xv. It can be used as follows: