Rating: 6 I think the one thing that makes this look so plain is the fact it's the same base grey for the terrain as for the tank. If you don't want to add camo or unit markings, try just taking a pic on a different coloured background.
Rating: 6 The Idea of the exta armour is not so bad, the problem is a lot of "unstructured" undetailed surfaces. Maybe is the 2- or 3-colour camufalge scheme the best?
Rating: 4 It's very plain, and doesn't look like the people making the tank spray painted it at all. You'd really help your score by painting some colors and symbols on it. If you don't like the idea of red, or blue tanks, use a camo scheme.