Well, I've got some:

• The logo could look better with a more minimalist approach, in my opinion, Cryptocoin is kinda flashy, D logo looks nice.
• Menu looks old, could use a nice, simple one, with changing color on hover.
• The question mark would also look nice if it could fade out or in on hover, would make it look more of a button.
• Had trouble finding the Control Panel to check my account, would be nice to have a login bar at the top, that after login, shows some account related links.(
• Site would look better if centered(and responsive). On a wide display, it just sits to the left.
• When you first land on the page, would be nice to see some random listings, maybe sponsored ones or something, rather than seeing an empty box.
• Some banner boxes here and there to show website owners where can they advertise would be nice.

Just some stuff I saw on first glance, please don't regard these as critics, just my view of things that could get improved. I like the concept and I'ld like to be one of the first to get a banner up .