The Dink Network

They just need converting to .bmp to use. But thier shadows are done with the alpha channel instead of the black and white grid like dink graphics. You might get fairly good shadows with a program as simple as MS paint by converting to .bmp ( several programs can do that), open with paint, inverting colors, paste a shadow grid over the shadow area, and invert colors back to normal.
(This trick is assuming the background ends up white after converting to .bmp . If they end up black, inverting isn't needed. )