I have pretty much always used the matching quilting thread all over a quilt top, so that the quilting adds texture. I have several quilts which need to be quilted, and they will probably get the same treatment … the treatment they were designed for. New projects are going to get different right from the start … background space for quilting will be included, and some of that background might even get a contrast thread on it, with matching thread used in the spaces which need a bit of boring fill-in quilting to even out the quilting a bit.
In the design above, I would cross hatch the background area where there are no quilting lines added.
By the way, did you know the best way to mark cross hatching, and any other straight line quilting for hand work is to use a good quality masking tape. Don’t leave the tape in place overnight, but you can reuse the tape until it stops sticking down properly.