When comparing Eye of Gnome (eog) vs Viewnior, the Slant community recommends Viewnior for most people. In the question“What are the best FOSS image viewers for UNIX-like systems?” Viewnior is ranked 4th while Eye of Gnome (eog) is ranked 9th.
Ranked in these QuestionsQuestion Ranking
Pros
Pro More lightweight than other kde or gnome dependent applications like gwenview, gthumb or kphotoalbum
Pro Double-click to view Fullscreen
By default, double-clicking on the current image opens it in Fullscreen mode. This can be turned off in Preferences if desired
Pro Image Slideshow
You can view a slideshow of all images in the current folder, and adjust the delay between images in the Preferences dialog
Pro ESC key exits Fullscreen and program
Pressing the ESC key exits Fullscreen mode, as well as exits the program ... hence press the ESC key twice and you're out
Pro Can set image as wallpaper
You can set the current image as your desktop wallpaper directly from within this program
Pro Lightweight design
Pro Minimal interface
Pro Fast
Cons
Con No APNG support
And it won't be it seems https://bugzilla.gnome.org/show_bug.cgi?id=151281