He should have a hide on the cool and the warm side. BP's like to hide so its nice for him to have the choice of hiding in a cool spot or a warm spot.

Also if you buy a thermometer make sure its a digital one. Not sure where your from but if from the US you can go to walmart and pick up a digital thermometer called an accurite. It has a sensor on the unit and one on a cord you can put somewhere else. So you can just stick the unit on the cold side and run the cord to the warm side and put the sensor on top of the UTH that way you can measure the UTH's temperature accurately and make sure your not burning your snake and also see what the ambient temperature on the cool side is.

Do you mean bark for the substrate on the tanks floor? I don't use bark I use newspaper or paper towels makes it alot easier and cheaper to change when they do they're business. But there is alot of different options out there.

background pictures that would be just for you. If you want to put one on to make it look nicer go for it. But I don't think it will make a big difference to the snake. But then again I did go to a reptile zoo last week and the lady told me a snake whisperer came in and said her reticulated wanted more greenery.