It took a bit of surfing around the walmart.com site to find the right place to send an email. Look at the bottom of the page and click "contact us". Then go to "email Walmart Stores" and there is a comment section. That's the only place I could find but I think that the email only goes to the actual store and not to corporate.
But anyway, I did my best and complimented them on the good service, value and selection at the fabric department.