I used to get a live Christmas tree for Fizz every year. We'd get a fraizer furrr with the round needles and make sure it hadn't been treated with fire-retardant or anything. I'd wash it off really well outside and let it dry before I brought it inside. I'd also only decorate it well above 'bunny level'. Everything below that was for Fizz. Sometimes I'd hang a plastic 'bunny safe' ornament on the lower branches for her to harrass. She loved laying under the tree and pretending she was a little wild bunny and she also loved nibbling on it. I always made sure that its water stand was covered so she couldn't get into the water and otherwise just kept an eye on her. Before Fizz I used to do it for my previous bun, Georgie. Never had any problems and it made both of us happy.
On a side note, watch out of Christmas flower plants. Poinsettias for example are dangerous for nibbling buns(and cats).
First two pics of Fizz, last one of Georgie and an ornament she stole off the tree the first year I had her before I realized how nosy rabbits were.