I think it's generally ok to use the watermarked web versions of stock images in mock-ups.
Of course if you decide to make a poster version of your image challenge entry, the correct thing to do would be to purchase the print resolution versions.
That's what I'm going to do. Yes sir.
( ,
Wed 17 Jul 2013, 23:15,
archived)
That's what I'm going to do. Yes sir.