Your painting and texturing skills are above superb. The way everything shines through is amazing, and the effort put into this is... amazing. However, ... The concept is original... but... it isn't that great. It seems three or four types of styles are emerging from this single picture, or perhaps it was created by a conglomerate of species/companies, rather than just one. the chest/ midriff looks carved from granite/ solid block of metal, and the arms look like they were pieced together from random bits of various types of scrap metal. The legs look like legitimate machinery- steam punk style, while the head looks totally and completely alien, maybe even as though one was inside it like a body suit, rather than a mech. Overall, they dont really add to much to each other. Also, on the whole, it seems rather top heavy. This is because the arms are so far back on the head, and the legs don't have enough of a backwards angle to make up for this oversight.
I really like the proportions and the big "backpack" like back. It's just great and seems like it has loads of live protecting stuff in it.
Also, it kinda feels like it could transform into a tank or something, which is not intended, but I like the idea of mechanical only look alike soldiers that can change their appearance to fit the needs.