You know what's my Linux image and PDF viewer in a pinch? Firefox.
I spend a lot of time in Firefox anyway, so it's often quicker to Ctrl-T to create a new tab and Ctrl-O to load local images or PDFs from ~/Pictures, ~/Downloads, or ~/Documents. Of course it works with other browsers too.
@tetrislife Just install a sufficiently old version, which probably can't open PDFs. 😀