Hello, I am a full stack developer. I have noticed that the site (itch.io) mainly uses PNG, JPG, and GIF formats. All of these are not the most optimal formats for a website with many images and high traffic. I suggest converting all of them to WebP format with 90% quality. If you prefer lossless transparency, you can convert them losslessly, but 90% quality is almost identical in appearance. A simple change like this could significantly improve the site performance.
You can achieve this by implementing a conversion process using a library that automatically converts all user-uploaded images to WebP format during the upload process. Alternatively, you can allow only WebP as an accepted upload format directly.

If you need assistance with this, feel free to contact me here for more details or suggestions regarding optimization or integration for the website.