In this article about a wall-building robot we see another step towards automatic construction, moving the 3-D printer concept onto the grand scale. This is very interesting and could be expanded quite a bit. It notes that arms could add texture to ceramic walls, but I would go further.
Why not create a texturing head which consists of strong metal pins on high-speed servos. You could drag this over the surface of maleable material, moving the servos back and forth under computer control line raster lines. This would allow the generation of any digital image in 3-D on the wall to a limited amount of depth.
You could do simple things like textures, or pleasing graphics of plants or nice patterns, but sculptors could also generate interesting forms of art for people to place in 3-D on their walls.
This could also be done on modern drywall. A set of rails could be mounted on a wall. A robot would run on the rails, first applying stucco, then when it is at the right consistency, run the "print head" to place patterns or sculpture into the stucco.
You might be able to do full 3-D printing though I see that as harder to do on a vertical surface, by having a "stucco-jet" with various coloured ceramics in the pipes, and individually controlled pumps to push out the right material at the right time, possibly for further shaping by the servo-pins, though I suspect they would be better with monocolour.