This is the progress on my Sherb's house. He still hasn't changed his wallpaper, and he now has an old-fashioned alarm clock in his house as well.
He always comments on really liking the furniture and color choice that I give him. The furniture I give him is based on the furniture in his actual home, so I don't know if that's why he always comments that he really likes it. I've tried changing the wall clock, but he will not change it.
Anytime he puts something up in his house, he'll comment that he'll look for a place to put it in his house. If he likes it, but won't put it in his house, he'll comment that he really likes it and he's glad that I gave it to him.
I'm not sure if they can change their walls, flooring, and anything hanging on their walls, but I'll keep trying.
Edit: the best way I found to go about it is to choose furniture for them to replace that is the same size as the furniture that you want them to move. He always replaces exactly what I want him to replace when I give him something of the same size.