Nice entry! I like the sense of a scene and narrative you have created, it definitely tells some epic story.
Compositionally I think you could do a lot more to bring more power to the image itself. You have arranged all your main elements of interest along the edges of the canvas, your focal points are equally distributed along the edges, but the lines of you composition all point towards the center of the canvas. So the resulting strange effect is that I want to look at the interesting bits, but my eyes keep getting pushed into the emptyish less interesting central area.
I dig the main castles on the cliff, though perhaps a bit more atmosphere to separate them from the cliff in areas could have worked well. In fact I like them so much, I wish they were the clear primary focal point and we could see more of them. I can see you've used a lot of photo textures, and one thing that needs to be done really well with this technique, is proper integration. You have done a decent job for the most part but I feel that the textural density of the photographs are perhaps a bit too detailed overall, and a bit more painting to simplify on top of things could help rest the eye and help with the slightly collage-y effect.
Interesting comments, I was quite blown away by this. I think it's more of a take it all in at once type of painting. Hence pulling you to the middle. Hmm, perhaps a ship sailing out in the centre would solve this? Love the details, like the female statues to the left. And the sun shining through on the right is gorgeous. Just a little nitpick, if you look at the bottom left 1/4 way in the ground is significantly blurred but the rock and grass beside it is very much in focus which looks a bit odd. Wonderful piece though, you should be proud.