I have over 300+ products on my shop and we are constantly adding more. I'm not happy with the quality of my photos when they show on the gallery's thumbnail. Once you click on the item and get a larger image the quality is fine.

A friend suggested I upload the images in png instead of jpeg but I don't want to sacrifice my page load speed. I'm even trying to find a way to speed up my load speed.

Any thoughts or suggestions will be highly appreciated.