What are some alternatives?
When comparing FileOptimizer and Caesium Image Compressor, you can also consider the following products
ImageOptim - Faster web pages and apps.
pngquant - command-line utility and library for lossy compression of PNG images
FastStone Photo Resizer - Convert and Rename images in batch mode Support JPEG, BMP, GIF, PNG, TIFF and JPEG2000
ImageMagick - ImageMagick is a software suite to create, edit, and compose bitmap images.
XnConvert - XnConvert is an easy image converter for graphic files, photos and images available on Windows...
Free UPX - Graphical interface for the UPX packer, UPX 3.91w, UPX 3.92w, UPX 3.93w, UPX 3.94w, Ultimate Packer for eXecutables, EXE packer