Inconsistent perspective. Each element is suggesting a different eye level which makes them look a bit wonky and as if they're falling back or sitting. Also i don't get the arm position, unless they're supposed to be holding weapons. Chest and head look like the eye level is behind them, waist and pedestal suggest above knees, knees read as if the level was below knees and ankles are telling it's above ankles.
Perspective errors are very evident because they have a boxy construction. Transformers' feet can be a bit tricky and you have two options. Either warp the feet at the ankles or give them more detail to add in a joint at the ankle. In G1 comics Geoff Senior did more warping to stand the characters' feet level on surfaces while Andrew Wildman attempted to keep a solid construction with the characters and at times the feet weren't level with the ground (if they didn't have ankles, like powermaster prime and grimlock).
Here's something to illustrate the perspective you're after.
The line is the eye level.
-edit-
Oh right, almost forgot. How about you make one completely new one while keeping an eye on the perspective and then everyone can help on that. It's a bit hard to critique a lot of stuff at once. Keep it up, i really like these.
