Colours, sizing, orientation, placement and transparency are all adjustable - and font is chosen from whatever you have available. Can throw in any other image too ... just not let it get too busy.
I am aware that some people might not like the visual intrusion - but the trade-off is whether you want you hard work pilfered.
One other point of interest ... I do a watermark for the photos I take for my seller, but do not do anything to photos 'borrowed' from manufacturers' websites. Sometimes, they just want to get an item listed and can't wait for my shots, so they use those from the manufacturer. My seller was in communication with a buyer who did not purchase one such item because 'the photo did not look like one of theirs"!!
Their (reasonably prominent) watermark had become a recognisable part of their 'branding' (for want of a better word) - with it, they attract sales, without it, they lose sales.