Optimize content and images

Hi,
last week I've seen a tweet from Kristof van Tomme (https://twitter.com/kvantomme/status/1138787651656519680) and was thinking about how our flagship site is environment friendly.
Have done couple of simple testing and the results were quite far from ideal.
https://www.websitecarbon.com/website/drupal-org/
https://gtmetrix.com/reports/www.drupal.org/CF5GigKj

Problem 1

On the second link you can see that one of the main issues discovered are images especialy the five case study images. Thea account for almost half of the data of the homepage.
Can we use JPG instead? I know these images are user generated content, but at least can we make some recommendation to use JPG instead of PNG?
Or if the casestudy is selected for being shown on homepage can some editor went in and resave the image from PNG to JPG?
I don't know how much unique visitors drupal.org have every day, but I suppose it will be thousands, so by shaving 1MB of data from the homepage we can possibly save GBs of data transfers every day. And if we look at that these images have expiration set to 1 day, I need to donwload these extra megabytes each day I visit D.O.

Problem 2

I've then looked at one of the case study and the results was unnecessarily even worse. More than 10MB of data to download. :(
https://gtmetrix.com/reports/www.drupal.org/1owZwzVs
All of these images are PNG, that is first part of the problem.
Second issue is that they are not using any image style, so they are shown exactly how the user uploads them. In case of the pinterest case study they are 1800px wide. But they are scaled down to 739px, or more tipicaly to 620px (3x less). If there is an image style setup to scale the image down for case study or even better if there is an resposnive image style.

Thank you for considering these changes.