For the floor pavement I prepared a map in photoshop and used it in 3D MAX for the mental ray displacement map. This time I did not need to increase the number of segments on the object. Displacement is calculeted in the render time only. I use this method for large areas.
For the doceration of the vault I painted my own ornaments but as always I say, I used a lot of refence photograps to learn about that kind of ornamentation (see images below).
Lighting and Camera Placement
Lighting is a part of design. Don't forget it or don't leave it to the end. Be aware of that light gives life and atmosphere to your design. And think of it in the very beginning. Make changes on the model if necessary to give the right ambiance of shade and shadows.
On the other hand the points where you put cameras and even field of views of the cameras are very important too. There can be very very small differences in the photographic composition but eye can feel comfortable in one but disturbed in another (see images below)
For architectural rendering somethimes you need to use a camera correction modifier to correct the verticle lines of the walls. Somethimes these lines can make disturbing compositions (see image below).
In this project I used a skylight and a mental ray area spot light to simule sun. In the vault, I put some very low strength spots to give light to the inside of the vault.
My render engine was built in mental ray engine in 3d MAX 7.5. I rendered this work in 3636 pixels on the vertical direction. Total rendering time was about 10 hours on a double CPU AMD Opteron with 2 GB of RAM. (see final image below).