Of course you can mix batiks in with other fabrics. I do it all the time. In fact I am working on one right now where all the back ground and sashing pieces are non-batik. Here is a link to a picture of a quilt I made that is about 80% batiks and 20 % non batiks (taken before it was quilted). There is absolutely no reason not to mix them up.
http://www.quiltingboard.com/t-24639-1.htm