Here are some fun ideas.
I did this a few years ago from Washi tape, and it turned out so good, we loved it https://www.justalittlecreativity.com/2015/11/how-to-create-a-winter-wonderland-with-scotch-expressions-tape.html
Here are a bunch of ideas here on Hometalk: https://www.hometalk.com/search/posts?filter=wall%20christmas%20tree
This is one I did for kids but it could be adapted for grown up spaces: https://www.craftylittlegnome.com/felt-christmas-tree/
This one looks amazing
I just saw some great ideas on Hometalk -- did you check around using the search bar at the top left? That'll turn up all sorts of great ideas for you.