ThumbZipper

ThumbZipper is an easy-to-use software application capable of creating thumbnails from a sequence of images, compressing them in a ZIP archive. It supports batch processing, which means that it can resize multiple files at the same time.
This type of software can be used for quickly putting together an HTML gallery, for example. It gives you the possibility to set the thumbnail width and height to custom values.

Doesn't need installation

This is a portable application, so installation isn't necessary. You can extract the .exe file from the downloaded package, copy it to any location on the disk and double-click it to launch the thumbnail creator. Also, you can keep it stored on a USB flash drive to seamlessly launch ThumbZipper on any computer.

Set the thumbnail width and height

The interface is not quite intuitive, since it doesn't have descriptions for all boxes. On the upper-left corner, you can set the thumbnail width and height, add frames, and make the images square.
In addition, you can include subfolders and tell the app where you want to save the new ZIP archive, which will contain all thumbnails. To add pictures to the list, simply drag and drop them (or their folder) from Windows Explorer.
Worth noting is that the original photos remain untouched during the whole resizing operation, so there's no need to create backups before using this app. Furthermore, you can preview file content by double-clicking an entry in the file list.

Simple and practical thumbnail generator

Unfortunately, ThumbZipper doesn't have an option for preserving the aspect ratio of the images by specifying only the width or only the height. Its interface needs more work to make it more intuitive. Nevertheless, the tool proves to be a fast and effective thumbnail creator that's also light on system resources consumption.