I did a google search & it seems like there are several manufacturers that make fabric that look like pine needles. This etsy store has several different kinds but there are more out there to choose from:
https://www.etsy.com/market/pine_needle_fabric
Here's a Christmas tree panel that you could make for your wall hanging. Personally, I think it looks a little to fake for me. I think I would make my own tree wall hanging from fabric.
https://www.nutsandboltsfabric.com/s...T-x2051107.htm