Important 'Why' Details
There are important rules to follow with websites but e-commerce adds some mandatory guidelines. It's all about facilitating speed and funneling by sight and function as quickly as possible to purchase.
No Distractions
So many websites now have enormous pictures on the home page with or without 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? Your homepage has the most valuable real estate. Use it wisely! Make sure they know how to buy --- and fast!
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 and a minimal logo is imperative. Don't make your visitors scroll since you have limited time to grab their attention.
Getting to products fast in order to buy!
Since the visitor is looking to buy, the more engaged the he or she is from the first second is important. So that's the function of the featured products and you can choose to have them at the top or the bottom of the home page. Having a row of them with the buy now button immediately tells the visitor what you sell and what you know will sell. (The buy now button does not come with default Zen Cart by the way.)
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.