I never understood what the bonus (%) was for on decorations and now I know why, in case you didn't:)! If you put decorations next to animals or things that you can collect money it will increase the amount of money you get back! So look for cheap things with a high bonus and place it around your animal etc. the blue square around the decorations shows you the bonus area. So you know if you animal is in the blue square, it has a bonus added to it!