In an old car I recovered the headliner and visors in dark blue velvet to replace the light blue cheapie stuff that was starting to fall down. After it was done and I got in, it was like a whole new car. I loved having the headliner dark instead of light! Made all the difference in the world. On that car the headliner came out as one piece of cardboard that had creases where it folded at the edges. Instead of removing all the old glue and foam I just flipped it and bent the flaps the opposite direction.
The one in the 'Bu, though, appears to be molded and won't be reversible, so I'll have to see what it takes to attach the new material to the old, or if I have to remove all the old stuff first. I've been planning to do this for a while. My idea was to paint the hard surfaces, but covering the pillars as well ........ hmmmm, that's something else to consider and I just might do that! I've got "Air Bag" molded into the B-pillar covers so I may need to paint them regardless, but the others qualify for material.
For color, my car is black on black on black. The only difference there is inside is that nice wood trim running around the doors and separating the two levels of the dash. I'm leaning toward a deep burgundy/maroon color. I'd rather have a deep forest green but thinking ahead about resale value makes me worry about that choice, since green doesn't seem to be a popular color among vehicle choices these days. Too bad, I wish it was!