Ordinarily if I were going to have two sofas in the same room, I'd have them match, unless it's a very large room with two different seating areas. There can be a problem in mixing grays as grays can differ greatly. Some of them may have blue in them and others perhaps brown. So if you must mix sofas, I feel it would be safer to go with black, white, or a color, unless you see samples of the current dye lot of the fabric to make sure the grays can live happily together.

I agree, I would not have another gray sofa. Choose another solid color. You may move sometime again and it is easier to have solids. Love the painting, a yellow sofa might look great and then you can add some of the yellow tones to the grey sofa and some of the grey to the yellow one to tie things together.