This is such a simple yet clever idea for a dollhouse!
Use an old bookcase or buy one at Ikea, use wallpaper scraps or why not craft paper to decorate the rooms.
I still remember my Barbie dollhouse :) I also had a car and a horse. But the best part is that my mother had saved all her Barbie dolls and clothes from her childhood that I just loved to borrow.
My cat especially loved a real fur coat that she would carry around and when she wanted to nap she could always be found on the second floor right over my barbie bed :)