If I possessed any sewing skills to speak of, the first thing I'd make is this dreamy striped picnic blanket by Anabela Piersol of Fieldguided.
Above: Made from cotton-weight canvas purchased for just $2 a yard and dyed at home, Anabela's blanket is a good reminder that DIY can do wonders for the wallet (just so long as you don't account for your own work hours).
Above: For a top and bottom layer, Anabela alternated strips of fabric that she dyed peach and gray—pale shades that she describes as "dreamy/cloudy/sky-like."
Above: A thin layer of cotton batting in between the two layers of canvas makes for an extra cushiony blanket.
Above: The final detail—a harness of soft cotton webbing for totability.
Above: Cotton twill tape secures the harness with tidy bows.
For more details about Anabela's process, see the full post on Fieldguided.
For ready-made picnic blanket options, see 10 Easy Pieces: Picnic Blankets.