I have finally succeeded (and gotten around to posting pictures)!
This is the project I posted a while back in the discussion section, because I just couldn't make the darn thing stick to my wall! I first tried using starch to adhere my fabric wall decal, but the fact that my "wall" was a slanted ceiling and the fabric was rather heavy made that plan fail. Then it was on to staples, but apparently my wall is pretty darn indestructible. Thankfully, I chickened out of using an actual glue (or something even more permanent like Mod Podge) at the last minute and instead used a combo of 3M poster hangers and good ol' scotch tape to get it up there. The tape is at the tips and some of the edges to help hold them flat, and the 3M wall hangers do the bulk of the sticking work.
It doesn't have quite the same finesse it did when I used the starch (before it all fell down), because I had a lot more control then in shaping the branches. I think it's still pretty darn good, though.
I also cut out stars and diamonds from old magazines and stuck those on the wall around the tree to add some colour. I'm so glad to finally have something filling that huge empty space. Now for the rest of the room...