In the interest of making Portableapps.com (and Launcher) as small as it can be, I have run all of the images from all of the folders through FileOptimizer - which is a front-end app for all of the cmdline compression algorithms. https://sourceforge.net/projects/nikkhokkho/files/FileOptimizer/ I'll be making a thread later to add to this platform. It's a great application. I use it every day.
I have only used lossless compression. File size was reduced considerably, and I feel it would be good to include these compressed images as part of the next update, or as part of current download source (not exactly sure if that's possible).