eiv is a GUI image viewer written in Go that is extensible with plugins.
By default it supports gif, jpeg, png, bmp, ccitt, tiff, vp8, vp8l, and webp.
go get -u github.com/patrickmcnamara/eiv
eiv $IMAGEFILENAME
To create a plugin for eiv for an image format abc, create (or download) a library that can decode that format into an image.Image in Go and register the format in the init function of your library.
Next, create a package main program in Go that imports your library and does not have a main function.
Build this using the plugin build mode for Go with an output name with the extension .eivp (e.g. go build -buildmode=plugin -o abc.eivp).
Put this plugin into your config directory under $CONFIGDIR/eiv/plugin.
Voilà.
eiv can now display your images.