Collection Preview Image

I am trying to make some collections for texture packs I have made, so I made one. The only problem comes when adding a preview image of the collection (which I really want to do), but whenever I add one, no matter the size of the image, it just becomes blurry. I don't really want a blurry image, just a nice clear image.

https://www.planetminecraft.com/member/hazzard588/ Here is a link to my profile page, and if you scroll down you will see a blurry Netherite Totem for the preview image. I just want to fix this.