I love these scrappies. They give a beveled look to the quilt. I think a meander would look nice or a loopy.

I love your scrappy. so pretty. i'd do a squiggly script L along the X

Made a couple of those trying to use up my scraps. Here's how I quilted it on my long arm. Since the quilt was in reds and blues, I quilted using navy thread so it showed up on the backside nicely.

I have used meandering on a string quilt just like that and it turned out fine. The busyness of the quilt calls for a simple design.

I would practice a new design on the entire thing in white, or pastel thread, so as not to overpower the white. The bold colors of the strings will mask any oopses and you'll be more confident with the design when you're done. I look at each quilting project as a snapshot of what I"m capable of at the time. If I don't stretch myself, I'll never get better.

White thread will be great.....the stippling on the midarm will be quick and really the best....
Happy midarming......
Love the white....I am on to trying this quilt with my strips...Thanks for sharing the white mid strip.

My first thought was a nice easy meander. Your white X's will still show up just fine. Since your intent is for this piece to be a utility quilt, let it be simple and stunning. Another other option could be a diagonal cross hatch. White/cream/gray thread would be just fine. It will blend in easily with all of your glorious colors.

I am far from expert, but maybe meander just the coloured parts leaving the white unquilted (or ditched), technically this should enhance the white elements. It is a lot of messing about though.

A meander is perfect for this quilt, it doesn't take away from the design. You could use a variegated thread, that would look nice to.
Sharon in Texas

Oh, it's very attractive but I'll leave it to others to suggest quilting patterns.