There has been a change made by eBay on the latest seller requirements. Originally eBay announced that watermarks would not be allowed on images from March 1st 2018, this seller requirement has been rescinded and will not go ahead.
eBay’s picture policy does not allow sellers to list with watermarks in product images they associate with their product listings. Although eBay are not enforcing the removal of watermarks from existing live listings, this could change and we recommend that new listings are created on eBay without watermarks. Additionally, any listings without watermarked images will rank better in eBay search, will surface in Google shopping search, and on eBay Partner Network affiliate sites. Any products containing watermarked images would not be eligible for eBay deals, promotions, and product-based shopping experiences.
These links will give you a further understanding of the change if you wish to read about it more in depth:
This article will be updated when eBay release a new policy change or update current policies: