My first thought when I saw this was eeeeeeeeeeeeeeeeeeeeee thagomizer! (I love that word). Beautiful stego :D And yay dinos! I especially love the balance with this one - you have a good eye for making me believe that the creature's centre of gravity is where it's meant to be.

As for suggestions for later, how about Cybertronian (war) tortoises? Or perhaps baby dragons nesting in unusual places. A pachycephalosaurus dinobot would also be really cool.