As has been said, textures textures, but I must admit one thing. YOU ARE ACTUALLY USING THEM QUITE OK! (compared) Seems like a rare thing nowdays. Just learn to make some, not just use the default ones.
When you learn that, you will also figure out how in the hell you can allign them correctly (comes with practise and error, mostly error).
As for the rest. You could have used a bit more details (simple ones) like some bolts here and there on the structures etc. Plus better lights. You do have soft shadows, but it still looks the piss. I know they are annoying to create, but the revard is even better (you'll get my respect biatch!).
You might not have the knowledge yet, but you certainly have the talent. You have the basics right, even a bit rough, but you have them right.