I want to be able to do something like this:
	xclock*backgroundPixmap:      /usr/include/X11/bitmaps/rootweave

You can't do this. The backgroundPixmap resource is a pixmap of the same
depth as the screen, not a bitmap (which is a pixmap of depth 1).  Because of
this, writing a generic String to Pixmap converter is impossible, since there
is no accepted convention for a file format for pixmaps.  Therefore, neither
the X Toolkit or the Athena widget set define a String to Pixmap converter;
because there is no converter you cannot specify this value as a resource.
The Athena widget set does define a String to Bitmap converter for use in
many of its widgets, however. 4/90]

However, note that a specific converter which encapsulates much of the
functionality of the xloadimage package by Jim Frost was posted 12/90 by
Sebastian Wangnick (basti@unido.informatik.uni-dortmund.de); it permits
loading of a number of image formats as a pixmap.