Truespace 3.2 is free.
If it is a fire breather, it should have a skinnier barrel.
If it is a rocket launcher, it should have a launcher.
If it is a ww2 tank, the barrel is just too large by more than double. More like triple or quadruple. The ratio of the tank barrel to the turret width really should be corrected.
If it is a near future tank, it should especially have more slope. Look at all modern tanks, especially the heavies. None are boxy. They need the shape to help deflect rounds. WW1 tanks were often boxy. ww2 tanks were more rounded. Modern tanks are more hard and linear, but with steep slopes.
A scifi tank would probably be an extension of a modern tank, with perhaps a nod to the a retro style (just for fun), but should not be a box.
My mistake on the treads. But, no matter what they were modeled in, they need to be flatter on the bottom or it is more of a rocking horse than armor.
Here is a quicky I threw together in Bryce.
I based it loosely on yours.. with a round turret and a boxy chassis, an odd combination. Plus the barrel is over sized... and there are some sort of exposed containers on the back end.
I made the turret lower and put a few more angles on the chassis.
Just food for thougt.