SuperJPG

High performance image file viewer and cataloguing utility.

It features fast thumbnails, drag and drop sorting, directory management and keyword indexing.

You can copy, move, rename and resize image files, or whole directories.

Use powerful printing functions for individual images, thumbnail sheets, or batches of images with specific sheet layouts.

Perform colour adjustments, sharpen and soften, rotate, crop, and fix red eye!Includes a built in slideshow with transition effects, and more.

Create index images and View GIF animations.

Supports JPG, GIF, TIF, BMP, PNG, PSD, PCX.

The big advantage of this software is that you can easily open and resize multiple images to fit to the available screen space. Most thumbnail viewers will only let you open one image at a time and lack the ability to use the full screen with more than one image.

This application is abandonware (company went bust in 2004) but it is so useful that I still use it today (on Windows 10).

It doesn't deal with unicode filenames. Other than that it seems to work fine with modern file system conventions.

Won't animate gifs in resized viewing windows.