Nevin asked me to comment on a question about using the computer to try new upholstery on a photo of a piece of furniture. Pardon me if I have posted in the wrong place. Here's the quick version of what I did on this sofa.
The image software I use is Corel / Jasc Paint Shop Pro. It is pretty much the same as Photoshop, except better in some ways and $500 cheaper. On an early image, before refinishing, I used the Clone tool to sample a clean area of upholstery and clone it onto an area that was torn or smeared from stripping. Clone vertical surfaces to vertical and flat to flat. The result was clean, repaired upholstery.
For the half-'n-half image, I increased the canvas size to make room for another image, then pasted the image we took from a factory advert next to it on a different layer. I then juggled layer sizes until my image and the advert were the same size. Next I used the lasso tool to select the work area to prevent spillage onto the wood. Next, I cloned the factory upholstery onto the new image, within the confines of the selected area.
For cleanup, I cropped down to one sofa and then used color filters to change the color of the selected upholstery from grayish to anything I wanted! It sounds complicated, but it only takes a few minutes if you are familiar with the tools.
If you do not have a clone tool, you can manually select chunks of upholstery and manually paste them into place.
If the upholstery is light and fairly uniform, surrounded by dark wood, you can sometimes just use a flood fill tool at around 30% density to dump in a pattern or color, whilst retaining contours.
If I do this for a catalog, I have to be sure to make it obvious that I am tinkering, lest someone get the idea they are getting upholstery! I like to see a piece with good upholstery (to make a pretty picture), but a lot of serious antiquers like to cut furniture open to examine the frame for condition and authenticity