So, I have a watermark on my galleries, which helps notify users that my work is copyrighted and FOR SALE... cool.
Now, as a photographer, I want to make MY LIFE as easy as possible, and I've found that having my copyright/watermark at the bottom right of the images works most of the time; HOWEVER, there are times people wish to crop or change the image, to where a portion of my watermark (on the uploaded image) is cropped funky.
So, my suggestion, allow the photographer to upload WITHOUT ANY WATERMARK... and, when the end-user chooses to purchase images (from the 'watermarked' gallery (as set in the gallery watermarks overlaying the images)... the photographer CAN CHOOSE WHICH AND WHERE their watermark will appear on downloaded, and printed, images purchased... as photographs are ordered.
So, for example, a 'personal use' download might have the photographers name/logo watermarked in the lower right... but a 'commercial use' (which is priced multiples more) might not have any watermark on the image at all (solely at the photographers discretion).
A 4x6 or 8x10 might have one watermark, but a 20x30 or large canvas might have none or a completely different one. SET BY THE PHOTOGRAPHER... determined by the photographer...
And their could realistically even be another setting option PER IMAGE, $xx.00 for the image with the watermark, and $xxx.00 for the same image without the watermark; which only commercial clients would likely select... but, it's a very real and potential passive upgrade to the sale.
Having this 'upon use' option for different watermarks could be pretty easy to set up, though it could take a bit of time in planning. It could be per product... type & size... as well as assorted other factors, that could also be taken into consideration... such as a 'coupon code' that turns off/on the watermarks for all prints or all downloads for THAT specific ORDER.