Since a long time I wish I would do this but now it's done. All static images have been optimised using mozjpeg or zopfli.
We save 24.7% space. I made some benchmarks on Hoa's homepage, and here is the result.
We save 14.49% of the homepage size. This is a good improvement !
The map images are under optimisation. It takes longer and my computer is starting to fly, but it's fine. So far, we save between 14 and 20% of the space. I will update the map images as soon as the compression overs.