gPhoto is a program and library framework that lets users download pictures from their digital cameras. The libgphoto2 library gives you access to hundreds of models of digital cameras on several platforms. GIT repo and Issue tracker lives at https://github.com/gphoto/ these days.
A full featured cross-platform image library
Developer's Image Library (DevIL) is a cross-platform image library utilizing a simple syntax to load, save, convert, manipulate, filter and display a variety of images with ease.
Comix is a user-friendly, customizable image viewer. It is specifically designed to handle comic books, but also serves as a generic viewer. It reads images in ZIP, RAR or tar archives (also gzip or bzip2 compressed) as well as plain image files.
The "Java Mass JPEG Resizer Tool" has following Features Resize all JPEG Images of a Directory, Create Webgalleries, Pack it to an ZIP File for E-Mail Attachments. The Tool is available in German and English.
Project moved to Bitbucket https://bitbucket.org/andreyu/simple-viewer-gl Small and simple viewer for Linux, support multipage images, support transparency and alpha-channel in images.