On the left hand side of the screen are two boxes - the lower one has a heading "Sell Your Photos" and you can create your account there. The one above allows you to create an account to buy the photos - could you perhaps add a heading "Buy The Photos"? I think it would just make it a little more obvious what that box is for - besides creating a lightbox!
"Sell your photos" - that tells you immediately what will happen there but the other one makes you wonder! Hope I am not being too dense about this!