Presumably you could get some/all of the pictures from some of the previews?
The artists themselves offer their maps/art for sale on their own sites. Official release is the 15th(?), so I think you have to wait until then.
And I just got this from Mike Schley's site:
As you may already know, the new D&D adventure Out of the Abyss sees it's worldwide release today. To celebrate, I've created a coupon for returning customers that can be applied to any digital downloads in the shop. Just enter the coupon code TheAbyss during checkout and get 15% off your entire purchase. Bonus: You can use it as many times as you'd like before it expires on September 30th.