I started with the nursery, and painted the walls as close a match to the wallpaper as I could, and then cut out the balloons from the wallpaper and stuck them on upside down. Did something similar with a mixture of paint and wallpaper in the pink room - was quite proud of the results!
and the kitchen
The lights are battery operated so no need to wire them in.
The window seat I change occasionally, sometimes with flowers and champagne, and at Christmas it had a small tree, champagne and fruit meringues!
All of the fourth walls are now finished, and I think it makes the house look a lot more finished.
My next task will be to decorate it for Halloween with all of the pumpkins, candles and toadstools I've made from polymer clay.