Forcevision Image Viewer
Forcevision is an image viewer and image manipulation tool that is available free for non commercial purposes. It supports 46 different image formats and is able to convert single images or multiple ones in batch mode.
Has most of the features that programs like irfanview have, like thumbnailed view, manipulate settings like brightness and size, flip images and adjust colors. Best of all, its free and fast to use. An alternative to irfanview and xnview.