The Dining Room was actually just a red brick glassed in porch with a grey painted cement floor.

The cement floor was stained to resemble marble.
The red brick walls were covered with shimmering plaster.
The ceiling was covered with a painted canvas of faux gilded mosaics.
The moldings were wood grained for a rich look.
Window sills were handmade /decorated of plaster.

These are just some of the many transformations done by the artists.
For an up-close and more detailed look into how some of these techniques were done, check out

The House that Faux Built: How to Transform Your Home
From Shabby to Showplace
Using Paints, Plasters and Creativity!
by Adrienne van Dooren