The ground texture was done by hand in photoshop. As you can see, there is tiling, but it is not noticeable on the camera, so it works.
I modeled and textured a big column to add depth to the image. I used it several times later on the final composition.
I rendered the ground in RPF so I could have control over the depth and the fog. Combustion can do a great job on static images, not only for video or animations. Be careful, a big RPF is a ram-eater, and combustion has no mercy with low-end computers.
Those are the layers in photoshop. There are a lot of tweaking here and there. Almost all the texturing has been done here. I used lots of images and textures to create fire, smoke, clouds and dust. I did some cloning jobs to fix mistakes on the render. Also I rendered some more characters to give more dramatism to the image.
I have created a video file showing each layer being added to the composition. Watch it frame by frame to see how everything works. Watch it
Thanks for reading. I hope you have learned something about what you should and what you shouldn't do when creating a complex scene