It’s always important what choice you make for a website background. Using a huge image is a big mistake because it will slow down your page load time and also might not always cover the space you want it to effectively. The best backgrounds are made from seamless patterns and below are a few resources on where to find the best ones!
Pattern Cooler lets you take one of its many designs and completely customize it with your own colors to match your website. This is a great solution for most backgrounds and allows you a lot of freedom to control your colors.