VirtualBoxImages.com

gThumb is an image viewer and browser for the GNOME Desktop. View single images (including GIF animations). Supported image types are: BMP, JPEG, GIF, PNG, TIFF, ICO, XPM. Browse your hard disk showing you thumbnails of image files.

GQview is an image viewer for Unix operating systems (developed on Linux). It's key features include single click file viewing, external editor support, thumbnail preview, and zoom features. Some image management features are also included.

Note that GQview requires GTK 2.4 (link below).