Googled Cajun Field and clicked on images.
Yeah the big M is large "gravel rocks" if you can call it that, they paint it white and it seems to be a very easy way to make a big grass hill look nice. Imagine walking out of the tunnel and you see that big "L" or "UL". I think it would be really cool.
p.s. Didn't mean to hijack all of the pressure washing. Let the hilarity continue!