ps backend with images in cmyk

I'm experimenting with a customized ps backend that saves images in
cmyk colorspace.
It simply converts the rgb image to cmyk (using lcms), and nothing
more (i.e., it does not embed the icc profile inside the eps file).
While I don't see practical usefulness of this other than for a
previewing purpose, give it a try if you're interested (the current
svn matplotlib is required).
Any comment of suggestion will be welcomed.