Here’s an excerpt from your image file request mail for when someone is to submit their assets images to the marketplace.
I love the png format. It’s lossless and relatively small for being so, compared to other formats. It also supports alphas. As a web-designer by day, I use png almost exclusively for website graphics.
But using it for the marketplace images is not a good practice. Those images are often way too large and complicated to be good candidates for the png format. They also don’t need to be lossless or have alphas. The featured and thumb images might get away with being png on account on being smaller, but the screenshots don’t, unless they all have a large portion that is a single color background.
Instead, you should really use jpgs for these. That format was made to be optimal for large, complicated images. They’re not lossless of course, but they do a much better job at keeping good quality over using something like tinypng.
I had a 1920x1080 png screenshot that was 1.58MB in size.
When converted to jpg at quality 10 of 12, it became 346KB with hardly any noticable loss in quality.
When I tried tinypng instead, it became 453KB and the dithering made it look like a gif from the late 90s.
The above criteria from the email will make all content creators scratch their heads on how to solve it without compromising the quality of their work. Imagine making a photorealistic fire effect, taking a screenshot of it only to have it turn into a dithered mess in seemingly 256 colors to pass these criteria. It’s unnecessary headache. Just make it easy on us and allow jpgs instead.