The mechanics of it look solid, but as you say could use a little more work - perhaps with some surface details on a few of the flat parts, and a bit more contrast to show some detail in the shadows. Unless of course you add a back & foreground in harsh sunlight with some smoke, dust or a foggy battlefield element, then the darker areas would be fine.
More to photograph them...mostly for my Mad World illustrated novel project. It doubles for home defense too, but I'm not all that concerned about that. Actually I own more melee weapons than firearms...more exotic combat knives and swords, etc. than I can count, lol. Mostly they just decorate my studio and get photographed for an image on occasion...oh, and occasionally I have to kill a zombie possum....West Virgina has a lot of those [link]
I like the design. There is enough detail right now to get a good feel of the robot and I like that youput the soldier in for scale. Only the legs are noot really finnished enough to really get a good idea of their form. Would be nice to see it refined and coloured. Nice work