Putting taps on top of a freezer can cause some problems. One, it's hard to keep the lines cool so you'll probably pour a lot of foam. Second, when you need to open the freezer you may have to move it away from the wall or your taps will hit.
I started with a tower on top of mine, but after a year I built a wooden collar instead and mounted my taps in it. I'm very glad I did that, especially when it comes to opening the freezer.