XnView MP
Free Personal
XnView MP is the enhanced version of XnView Classic. It is a powerful cross-platform media browser, viewer and converter.
Geeqie Image Viewer
Open Source
Geeqie is a lightweight Gtk+ based image viewer for Unix like operating systems.
gThumb
Open Source
gThumb is an image viewer and organizer with a couple of limited options to also edit images.
Compare Viu 2 with alternatives
Compare Geeqie Image Viewer and Viu 2 and decide which is most suitable for you.