Another thought, is doing this like how I create maps in Xara. I use premade map objects that I also create in Xara (furniture, trees, etc.) I also use textures (photo images) of marble, wood grain, dirt, etc. to fill the shapes I create.

So for your project, start with a scanned photo placed in Xara, then draw shapes for your railings, added wall pieces for marbling. Instead of photo textures, create your own hand-done marbling and other detailing specific to your project as its own art piece. Then use that drawn art piece as the texture image fill for your shape. That way you don't have to draw new marbling for every image you alter, you simply draw in the shapes of added structural content, and use you art to fill those shapes.