feh is an image viewer at heart, though it does other cool stuff.
feh features include simple image viewing, multiple image viewing
(slideshow), multiple image viewing in multiwindows, image viewing
in fullscreen, image list mode, loadable/unloadable listing,
recursive file opening, saving/loading filelists, loading images
via http, reloading after delay, montage creation, and more.

feh requires giblib and imlib2.