If you're going to take your time to stitch something beautiful I think it's worth using a great quality cotton fabric like this Kona cotton by Robert Kaufman. As well as embroidery, it's also great for doll making, dressmaking and quilting.
Weight: approx 140g/sqm (medium weight)
Available in a fat quarter (approx. 50x57cm). If you need a larger piece, by ordering 2 fat quarters you will get 50x114cm, 4 fat quarters will be 100x114cm etc.