Prefer blues, oranges and greys (but not all three are necessary - it can be a primarily blue design, or a primarily orange design, etc.). The main banner image on the homepage should be large and will change regularly. The left column will be a text-based list of categories, like on Amazon.com. The upper right corner should contain text links to "My Account", "My Wishlist", and "Help". The top horizontal nav bar should contain category links to "Men's", "Women's, "Kid's", "Designer" and "On Sale", with a search box either centered or aligned right in the nav bar, or directly above the nav bar. Below the main banner image will be two columns with products, as in Magento's default design. There should be a third column for other promotional images, like Free Shipping or Recent News, etc. The banner image should span all three columns. Below this will be some text, and below that will be a footer of text nav links.
The Category page should have a smaller but still significantly big banner image, followed by a three column display of category listings. The left column will have Magento's "layered navigation" and will be text based. The header and nav bar should stay the same, and the footer text links will remain. The product page will be the same, except just show a large product image with details below instead of the three column product listing.