as a "rescuer" of blocks ,_ I would put them on tea stained muslin OR cream on cream blocks, the centers would either be same as block OR I would take them shopping, visit "AUNT GRACE" & her friends and pick out a color, that blended nicely! Your background blocks should be several inches LARGER than the diameter of your circles. If you want sashing between blocks I would use the same fabric you pick out for the centers, keeping it on the smaller size, possible cornerstones of background color