I had to totally repicture an ad that had sold about 55 identical items both in Aust & Internationally since mid 2012 because of the ebay photo requirements being x times pixels.  I needed to upgrade the listing to allow for recent AP post price rises on supposedly "Freepost" which is actually postage included.

Mine had no watermarks etc, but were scans (of a commemorative medallion). My new photos now have none of the resolution that the scans did & my rankings on this item have dropped to last on Best Match lists due to now listing states 0 sold. I also resent having had to spend half an hour repicturing, cropping,  & adding new pics, when I was only adjusting postcost, & now the pics look so carp even I wouldn't buy (& I know what the items really look like!)  Level playing field indeed! PPfft!