nomacs is an image viewer that is small, fast, and able to handle the most common image formats including RAW images. It also makes it possible to synchronize multiple viewers on a single computer or via the LAN, which is useful for comparing images and spotting the differences. This is useful for architects who want to see their progress, for example.
vvvP (Virtual Volumes View Photo Edition) catalogs photographs on removable devices and hard disks at the same time. Images can also be arranged in a single virtual filesystem. Each folder of this filesystem can contain images from many disks. The program allows you to view image thumbnails and full images.
Crossbow is an image browser and viewer for Mac OS X similar to ACDSee on Windows. Some key features include a thumbnail image browser with preview and an image viewer with a full-screen slideshow. It supports all Core Image file formats including JPEG, GIF, PNG, TIFF, PDF, and raw. It displays image metadata including EXIF, IPTC, and GPS. It can create zip archives. Planned features include batch resize, rotate, convert, and rename, the file operations rename, copy, move, and delete, and copying images from the camera.