Designing site navigation involves finding a balance between the importance of making it noticeable and not overpowering content by standing out too much. This question is about achieving that balance. The usability of the navigation will be left to the next chapter.
Navigation is not the place to show off your Photoshop skills unnecessarily.
Plain colors, slight gradients, or subtle light effects are much nicer, yet still effective. You need to strike a balance between making it clear where the navigation is and not making it the center of attention.
Using icons instead of words in your navigation not only requires visitors to think too much, it’s also more visually distracting. Your eye is naturally drawn to images and having a group of five or more of them at the top of your website is particularly distracting. You want people to notice the navigation, but you do that by the overall design, not icons.
From a layout standpoint, should you put the main navigation above or below the logo? One common structure is to have the main menu below the logo and a secondary small menu above and to the right.
Consistency of design is important with navigation. You might change the look of your header for different parts of a website, but it’s best to keep the same colors and look for navigation.