I recently discovered this little application, and I must confess it nicely fits a niche. The Eye of GNOME (eog), is a kind of clone of the Windows default picture viewer, and is a good complement for other Linux tools like ImageMagick.
I use the display tool of the ImageMagick package for highly repetitive and/or precise transformation image watching (as in putting one image above another, then watching the result, then making the composition again if it was not OK, or resizing a set of images to a given exact percent of their original size).
On the other hand, eog is nice for watching a lot of images in a row, and having them automatically resized to fit in the watch window. eog also permits smooth scrolling with the mouse wheel, very fast image rotation, and single-click window fitting of the image.
Give it a try!