nomacs is a free, open source image viewer

nomacs features semi-transparent widgets that display additional information such as thumbnails, metadata or histogram.
It is able to browse images in zip or MS Office files which can be extracted to a directory.
Metadata stored with the image can be displayed and you can add notes to images.
A thumbnail preview of the current folder is included as well as a file explorer panel which allows switching between folders.
Within a directory you can apply a file filter, so that only images are displayed whose filenames have a certain string or match a regular expression.
Activating the cache allows for instantly switching between images.