If you pick a focus fabric in your earth toned background that has a few other colors in it, you can then pick some fabrics in the other colors. They don't have to match exactly, but they should blend well together. They can be prints, plain, marble, etc. Keep the pattern you want to use in mind. If there's a color that is really overpowering, you can use small amounts and it will give it some punch.
Look at some of the collections on the fabric manufacturers websites. You will get an idea of what looks good together.
Good luck!