The following example is an action definition for starting the Island Paint drawing tool. The icons Ipaint.l and Ipaint.s are associated with the action.
ACTION IslandPaintOpenDoc { WINDOW_TYPE NO-STDIO ICON Ipaint EXEC_STRING /usr/bin/IslandPaint %Arg_1"File to open:"% }
If you are using color icons, the desktop first appends .pm when looking for the actual icon files. Otherwise (or if no match is found with .pm), the desktop appends .bm.