Renters are making the condo association property look bad

Our condo association consists of 3 units each approx 1,000 sf . Two of three are rented out.  The renters place "decorative" items all around the perimeter of the building. Large flower pots, bird bath, angel statues, a large ceramic pig, large frog, etc...Isn't the outside area of a building restricted for placement of all these personal decorations?  The property is small, and looks very cluttered! Help!  How do we handle this?