Choose your design with your future growth in mind. If you want to add other features like email marketing or a shopping cart at a later stage, you would be best choosing a design now that caters for this rather than choosing one that doesn't and trying to adjust it later. The same rule applies for your future growth of content. You might only need 5 pages now but want to grow to lots more later, therefore, a vertical navigation menu might suit you better than a width-limited horizontal navigation menu.

If you need to publish lots of content heavy pages on your website try to choose a design that can easily cater for this. E.g. it's no good choosing a photography or similar design template full of photo galleries if you plan on adding lots of text pages to your website.