You can buy decorations to decorate your non premium businesses and houses with the introduction of version 1.4.0. Select the Hammer icon in the top right and pick a house or business and you will be taken to a screen which shows you the number of "decoration slots" a building has available along with a list of decorations you can purchase with bucks or coins. As of release the only free decorations are the berry bush and the thumbs-up.
(My Photo Stream in iCloud is broken so pics won't be coming till I can get it fixed - Sorry)