There seem to be a pixelation issue on thumbnails of images in portrait format (and/or with small cliparts as well? Or was that solved already?). These images may point out if there is a problem. Proof image that it is the image's width/height ratio, and not the size. #217894 was 600 px / 24000 px, while this one is 10 px / 400 px, showing the exact same pixelation.
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thumbnail testing free icon was designed by Lazur URH for icons Png and presented to its users.
Lazur URH
2/22/2018