You don't need raster images for this. After all, the shapes are quite simple: they're basically squares. You might want bevelled edges with shading, in which case you can draw the block in its regular color, two adjacent edges (using line drawing) in a lighter color, and the remaining two edges in a darker color. You could do what I did, and use rounded rectangles. If you want to see if it looks good enough, the .jar file is
here, though I think you'll need to save it locally before running it.