Desktop Pictures in Windowmaker

[slack006]

Quick and easy folks: In Windowmaker (did I mention that WM kicks arse?), I'm trying to use some various jpg's for a background. I figured out how to make them selectable in the App menu and therefore easy to use. However, I cannot for the life of me figure out how to make the pic scale... (i.e. my desktop is 1200 x 1024, and the pic is 800 x 600 or somethin)

Anyone got a quick lead to an answer on this one?

Thanks much!