From what I've read on the Mesolithic, weaving was well established, so the grass cape would be appropriate. The main difference between Paleolithic and Mesolithic seems to be the disappearance of the megafauna, which probably explains the adoption of the bow over the atlatl as the game animals became smaller. I believe that clothing likely varied more by region than it did by time period. Much of Otzi's gear wouldn't have been out of place in North America 150 years ago. What works for a given climate works, and stitched clothing dates back to the Paleolithic. Textiles didn't become dominant until later in the Neolithic, and not until after Otzi's time, in northwestern Europe. That's evidenced by the fact that most of what he wore were skins. You could pull from a wide variety of sources and probably be accurate just by avoiding too many "modern" decorative practices, specific to NA peoples, like quilling and fringe. The term Mesolithic doesn't seem to apply to the Americas, I believe it's Archaic here. Artwork in Mesolithic Europe became more stylized pictograph, as opposed to the realism of the Paleolithic cave paintings, and more often depicted humans than animals. Some archaeologists see it as the beginnings of writing, like primitive hieroglyphics. I'm not sure what there is for any surviving evidence of clothing decoration from that time. Well, good luck with this, sounds like you'll have alot of fun. I used to do Medieval reenactment, but I had always wished there were Paleolithic reenactment groups.
