Programmatically changing wallpaper

[brian]

My wife has about a gazillion photos which she likes to use as her
wallpaper, and she also like them to change every few minutes,
selecting pictures randomly. At the moment, she insists on using KDE
and Plasma because that desktop can handle her pictures, as above.

I can't find any way to randomly change from a defined list of
wallpapers in XFCE. Am I missing something? If not, does anyone know
where XFCE keeps the details of the current wallpaper? I can easily
write a program in FreePascal to do the changing if I knew where to
set the name of the file. I've tried doing a grep from / downwards on
my PC looking for a file containing the name of the wallpaper that I
currently use, but there were no matches.

Anyone have any ideas?

Thanks,

Brian.