Wow ,y a very nice take on transformers. Good use of texture and colors.
However the levels are rather high all over the picture. There would be more room to the darker levels but maybe you intendet it like that.
Also backround could have a bit more contrast, even if it might be foggy here. Same goes for the landscape foreground. It feels like hes hanging in midair on groundlevel. Just a slight darkening gradient would make the ground much more "touchable" or present.
Hope I could help a bit though (Im doin nothin else than backgrounds :D ..)