Yes, flock spray is actually a great addition to any plain old christmas tree. It gives it a certain character it otherwise wouldn't have and you can make it a family activity if you wish. However do not overdo it because you run the risk of overbearing you tree.
This is a nice addition to a Christmas tree. If made correctly, with water, starch and soap flakes, it will look just like snow. Adding a little glitter after you add it to the tree is a nice touch.