My fortress- all things beautiful worth protecting

YIPPPEEEE!!!!! FINALLY UPLOADED WHAT TOOK ME ABOUT 14 HOURS TO FINISH!!!
What I used to make this:
A few pictures I found on google images (used as reference- not photomanips)
dirt brushes: [link]
blood brushes:
[link]
Smoke:
[link]
Ground/ grass:
[link]

The art side:
Ok, so, this is my first ever attempt to do a painting on photoshop. I used my bamboo drawing tab and did not follow a tutorial to make this, and this was made entirely in adobe photoshop elements. If you know how to do airbrushing/ painting on ps and you want to give me advise, you can, and constructive criticism is welcome also. Some questions to consider;
Is this looking (fairly) 3D??(Not like those new graphics super-realistic 3D art, but 3D as in you can see some dimension?) I did try and hilight the lights/ darks/ midtones, spent a long time doing so, and I hope it worked- I think it did, but then again, I'm not one to judge my own artwork after staring at it in progress for hours. I want someone else's unbias opinion.
I had this idea in mind for a very long time, and I never quite got around to actually completing it. Well, now, I did, and to be honest I'm quite happy with how it turned out, but I want to ask you whether YOUR eyes see it fit together. By that, I mean does it look like 2 pictures randomly put together? Because I was going to make it slightly different, but it just looked like 2 separate halves, so I had to change it and make the colours blend in more. But does it look like a whole or two halves??
Does the general idea work?? (To find out more about the idea, read on.)

The Historical side/ inspiration:
This was inspired by the film called "Fortress of Brest." It is a documentary about the Nazis' very first attack on Russia in WWII, showing the first 9 days of war in Russia. It truly is a sad film- and now, I don't mean sad as in "it's really sad because a few fictional characters die and that's so sad!" I actually mean sad as in PROPER sad and hard to watch, because the film is based on real facts and real people, and I'm not just talking about soldiers- children, mothers, sons and elders as well! I truly recommend anyone who is interested in History, or watching drama, to buy the DVD. The best things about this film is that it really does show that hope dies last, and it doesn't show everyone getting over emotional and crying their eyes out every second (although there are bits with tears) but instead it gets on with the plot and gives you plenty of action (of course, it does show emotions, too, but as I said, not crying every single second.) This is probably one of the best war films ever! And as well as that, it shows that even young people were allowed to fight, too! (The boy in this picture is young.) Not going to spoil any more of it for you- I really do recommend watching it! (google it for more info/ reviews etc)