There have been a lot of guesses. Some where dismissed. I don't think it's Walmart either. But according to the guesses so far they are Lowes, Home Depot, Menards, Window World, Walmart, Target. Oh and Springroll said (Bed bath and beyond) but I think he was kidding.
Some of those would be considered in the realm of Walmart as you stated. Other have the capability. But the PR said "NEW" customer as well.
Everything I say is my opinion. Do your own DD. It's your money.