BigStockPhoto has some limitations as well such as you have to be 18 years of age in order to agree to their usage rights as well as...
Without a BigStockPhoto Special License, you may not:
a. print the photo or image as a poster, postcard, greeting card, on a mug, shirt, hat, mouse pad, art print, painting, calendar, book, or gallery or use the image in screensavers, e-card software, web page builders or other systems where the image is shared or distributed to a number of users.
Is there a way to place a watermarked image into the files downloaded on sale and include a code or other option for replacing the watermarked image by paying for the images individual liscense for that particular website? Or is that just to hard to monitor?