Using XPDF as the viewer, everything else looks correct but the images are black.
It's my understanding that xpdf is basically unmaintained at this point. My distribution of choice (Gentoo) doesn't even offer it anymore.
Can you give an example of a file that you're having trouble with? I can't guarantee anything, but I can try to look into it.
This an example of it. http://hammackj.com/downloads/graphs.pdf
I wasn't aware that xpdf was unmaintained, the pdfs look great in preview/evince/chrome. I just got a complaint that they didn't work in xpdf and wasn't sure why.
Thanks for the report. I just tested with the latest prawn and xpdf 3.03-10 in debian and couldn't reproduce it.
I'll close the issue for now, but please re-open it if you have further information.