Similar Programs
To help you find the software that you need, here’s a comparison with other, similar image viewers. Neither of the following software can play an animation from an image file sequence so I left that out from the comparisons.
qView 4.0
Has a graphical configuration window with a bit more customization options. Has a somewhat different behaviour with image scaling and window resizing. Transparency blends into the background unlike in Emulsion where a checkerbboard pattern is used.
Image Glass 7.6.4
For Windows only. It has a lot more features than Emulsion and can be configured to show no UI elements other than the image. Unlike Emulsion it cannot open files which lack a file-name extension. All-in-all, if you are using Windows, you’ll probably find Image Glass more appropriate to use.
feh 2.23
For Linux only. It can do a number of things which Emulsion cannot, notably it can rotate and flip images. However the transparency pattern covers the entire window (by default) instead of only the image area as in Emulsion. It also has a ton of configuration and command line options.
sxiv 26
For Linux only. Can display a preview of all images within a folder and has significantly different default input behaviour.
Eye Of Gnome 3.28
For Linux only. Can rotate images, display their EXIF metadata, can set an image as the wallpaper, and has the option to open images with another program.