I put the spiky things on it's back, as you can see here. It is really starting to look right. At least, to me.
Then I added some plates to it's back. I need to fix the legs a little here because they keep splaying out awkwardly. Now all it needs are teeth, claws, tusks and eyes. These could make or break it.
And here is the finished creature. It turned out okay after all! I sent my nephew a picture and was told that "it's really accurate, definitely impressive".