Error 21919137: The resolution for provided picture(s) does not meet eBay's Picture Policy requirements.

All pictures passed in through each PictureDetails.PictureURL or VariationSpecificPictureSet.PictureURL fields must be at least 500 pixels on the longest side. Please review all of your pictures to see which ones don't meet this requirement. For those pictures that don't meet this requirement, remove them from the request payload before making another API call.