What about the
Simply Woven Pattern It has an old style picnic blanket style to it, so country feeling/western plaid feeling. You could incorporate the colors into the stripes. White background, purple stripes, gold (deep yellow) stripes, and blue stripes.
You could put a stripe/row of the footballs on the back, with maybe a total of 5 rows of fabric a purple row a white row, a blue row and a gold row, and the football row or, perhaps two narrow strips (2.5' before sewing) of the purple and white, then the football row, then another 2 narrow strips of blue and gold, with a green on the back for the football field for the remainder.
Things to check out if you haven't - what size, if he is going to pay for the quilt, and I wouldn't buy the fabric until you agree on price for it, and any additional needs - threads, time, backing, etc.