After an upgrade of my aptosid, it's work ! (epiphany 2.3.1)
Another user of my wiki me had report the problem (midori 0.4.4). I watch with him if it works for him also. (I think he used archlinux). (But on your forum an other user another user seems to have an identical problem http://forum.dokuwiki.org/post/30547
> Or does it happen with *every* JPG and PNG?
I tested with 3 pictures (one is attached), none had work.