I make scrappy log cabins all the time. One thing I like to do, if I use a fabric that is not as light as the others, I place it with a real light on either side.
and If a dark is more medium, I follow that with a true dark. Hope that makes sense.
I was making lc blocks today, with no/very little different values, I plan on using them as an applique background. Designing it in my head as I piece it:)