I could make a point for either satin or a cotton backing but I think satin, while it may be over kill, would be classy and go with the front.
On a side note, when I do a larger wall hanging now a days or one that will have some weight to it, I do two sleeves. One at the top to hang it from and a small thin one at the bottom to keep it straight, square and flat. I get the DH to rip a thin piece of wood (1/4 to maybe 3/8) then sand it smooth and slip it in . The edges never move or curl .... just a thought.