Getting to products fast
Since the visitor is looking to buy, the more engaged the he or she is from the first second is important. The best way to do this on nearly any e-commerce site is to show the potential buyer as many products as possible as fast as possible. So a short header - don't make your visitors scroll because you have limited time to grab their attention.
Any shopping cart is already image heavy due to products, so decrease the number of images used in the design. I also do not use the fast design solutions such as Bootstrap or other front end development tools that developers, not designers, love so much.
Forget slideshows. Think about it this way, do you ever go to a website and just sit and watch the slideshow panels? No? Well, why do you expect your customers to do it? Valuable real estate - use it wisely!
Width & Buyer Needs
100% websites are a thing of the past but with today's monitors, a fixed width site can look puny. So backgrounds give an illusion of 100% width but with a fixed width that may fit well on larger tablets when viewed horizontally. The point is that the old standard mobile first approaches simply ignores the needs and demands of a desktop computer. Too many customers still prefer to buy on their home computer to rely only on mobile.
Buy My Products Now!
Scream out, "look what we have for you to buy. Click here!" I've included the ability to choose where the home page center boxes are positioned. That feature is not turned on for this demo website as the text on the home page is more appropriate for my use so look at example below or this theme:
Light background - Any designer will tell you that dark text is easier to read against a light background. This holds true for print and web - and actually more true for web. This is especially true for the over 40 crowd who may have more difficulty due to aging eyes so making the website as easy to view as possible is incredibly important. And no, black is not more "restful" than lighter colors. I believe this push comes from young male developers - definitely not from true design principles. Of course, if you really gotta have it that way, I will acquiese to your demands.
3-D bars - I'm personally really fond of the 3D look of shadows so some of these designs feature that. It just dresses up things and is a simple thing for me to do with my software (I use Adobe Fireworks for web work - way easier than Photoshop). Quickie logos with shadows are also one of my "things".
Read more about The Five Most Important Things to Know About Shopping Cart Design.