Hi!
Indeed there's no image screensaver option - at least not yet.
My main focus at the moment is getting both OMX and the screensaver merged into the master branch so that we don't have to maintain two separate branches.
After that is done I may look into that at some point, given that it's something quite a few people have asked for. Just for perspective. Unfortunately, it won't happen in the very short term, but it would be on the roadmap as soon as I sort these two items out.
OMX is already submitted, just waiting for review and approval.
Hope this sheds some light. Thanks!