A newer, actually printable version is here: http://www.thingiverse.com/thing:1922547

I modified the script to support simple halftone dithering, so each pixel can have a gray value between 0 and 1, the brighter the pixel is, the bigger the hole created for it is. The picture has to be 75x75 pixels for customizer, if you want to use higher resolutions you have to download the scad file and use OpenSCAD to create it on your local machine. The image array can be created with this fiddle: http://jsfiddle.net/threonin/6dr8qu41/
It scales exponentially with resolution, so be careful, it can eat up lots of RAM very quickly.
If white_threshold is below 1 everything above it will be rendered as empty pixel, if you use it you have to make sure there are no dark patches surrounded by bright areas, as they would be free floating in the air then.
Everything below black_threshold will be solid black with no hole in it.
white_max and black_min can be used to limit the range of the hole sizes, so they don't become too small or the walls in between too big.
Cutoff is used to make the bottom flat for easier printing, set it to 100 if you don't want that.
You probably need to play around with these values to get something that is actually printable, I still don't have a printer so I don't know what is possible.
To preview the result you can use a similar setup as in the blendfile I uploaded.

Edit: I noticed the images were much too dark, I fixed this now, the old version is in stereographic_flat_dither.scad.old