Tall plants along the back but not right up against the glass. Have an inch or so of space between them and the glass.
Make sure you can see behind, under and all around the rocks and any caves they make. Fish food, waste and dead fish can get caught under things and rot. If you can see all around them, it's easier to keep it clean.
Some floating plants like Water Sprite or Red Root Floaters would add shade and reduce the algae that will grow on the glass.
More tall plants along the back. You have a light on the tank so maybe try live plants like Ambulia and Hygrophila polysperma. They are both pretty easy to grow and would help to cover the back of the tank.
If you can move the heater towards the middle of the tank (still have it on the back), it will provide a more even heat distribution. Alternatively have a filter outlet blowing water over the heater to help circulate the warm water.