I'm not sure what quality level you're looking for, but I know Bassett furniture can customize arms and skirts.

Amanda

Williams Sonoma Home features custom sofas on the cover of their latest catalog...

Here is a link that might be useful: Beekman custom

You can also customize a couple of sofas at Norwalk Furniture.

King Hickory is another manufacturer that allows changes - It's called the Creative Rooms Collection. I purchased sofas 16 years ago and have been very pleased with them. They do have 8 way hand tied springs and all American made.

Pearson has a personal preference program where you can customize skirts, arms, and the look of the cushions.

Hickory Chair also has a lot of options. They even allow you to submit your own skirt design if you know of something you would prefer over what they normally offer.

I think Century has a program as well, but I haven't used it before so I don't know as much about it.

I got a Key City last year and it was like a Chinese menu:
pick arms, pick skirt style, pick cushion style, etc.

Smith Brothers & Bassett will let you customize...arm style, skirt vs 3 or 4 leg types (not sure about skirt type), type of back pillows. I didn't find the Smith Brothers website to be very helpful compared to Bassett.

I posted today asking for a comparison of quality for these two companies.

Southwood Furniture has an excellent program which is very aggressively priced in the first four grades of fabric.. Its called Design Your Own, and typically a sofa will sell for under $ 2,000 in those first four fabric grades

Here is a link that might be useful: Southwood Design Your Own

Massoud will allow you to do this. I have several of their pieces and they are of excellent quality & have held up well in my active household. They make everything in Dallas, Texas!

Here is a link that might be useful: Massoud Furniture