There are plenty of ways to customize Windows. Some are free while other require you to purchase the software.
The most popular methods are by using Stardock products such as WindowBlinds, IconPack and other desktop customizing utilities from Stardock. They do have some free software but the majority of the good software you must pay for.
Another option is to create your own skins using Windows Style Builder by Ave I think it's called. This is also software you'll have to purchase. If you'd like more information on either of these avenues, I'd be happy to answer any questions I can, otherwise there are several members here who use these softwares frequently