Multiple images on root window with ImageMagick

I don't run a desktop environment, but instead use a bare window manager (StumpWM ). Thus, my usual method for setting a desktop background is to run display -window root from a WM startup script, which does what I want. When using multiple monitors, the X root window stretches across both and includes dead space. Thus, running that command line causes the image to either be stretched or tiled across the entire window, which isn't useful. I can use -geometry to display an image on either monitor, but if I run that again (to view on both monitors) it overwrites the other. There doesn't seem to be any ability with display to display two images in one invocation. How can I use display to display different images on both monitors? Alternatively, how else can I get the "desktop background image" effect without a desktop environment?