You can mix cottons and flannels, just be sure to prewash because flannel will likely shrink quite a bit.
As far as cotton and satin, you could mix those, but you want to be sure that the satiny fabric is washable and you should also test it with your iron, the higher setting for the cotton fabric could damage the satiny fabric. The satiny fabric will be harder to work with also, it tends to be slippery. If you are a new quilter you may want to stick with cottons and flannels to start out with, they are much easier to work with.