Doesn't a square-shaped gel "mask" on a regular spotlight work for this purpose? Haven't tried it, but I would think it would. Look into placing black & white shape gel images on your lights. Failing that, an actual "Barn door" object might serve to control where your shadow lines fall, and if you got really clever, you could build one with moving parts -- four angle-changing blades on the sides, post it to the web, and make a lot of people happy!! ---