I am a contributor as well as a customer. One of the benefits of using Dreamstime is the nice, large comp images they provide. It is very helpful. As a graphic designer, I frequently download comp images to see if they will work in my layout before I make a purchase.
On the other stock site that I use, their comp images are so tiny, it's hard to tell if I like the image or not. I have to show my client the mock-up before I buy the image and if it looks all bit-mapped and low-res, it can be hard for my client to visualize the end result.
I find myself coming to Dreamstime to see if I can find the same image for sale so I can get a larger comp. image. And of course, I purchase from Dreamstime instead of the competition.
Here are some beautiful cupcake photos I have downloaded comp images for and am considering using for a bakery promotion. Yum!