I would just set it in off-white or natural muslin or even poly-cotton broadcloth - just the usual squares and triangles with a simple border to frame it.
Tea-dying has been really big off and on over the years, but I think OxyClean takes a lot of that out.
If it feels like good quality fabric, maybe it would be worth putting some applique in the setting squares and triangles? It would be awful to put all that time into it and have the original pieces shred in the first laundering, though.