OK, I'll start the list and others can chime in!
1. A book on top of the toilet tank. Nobody wants to think of you sitting there taking a leisurely dump.
2. A can of air freshener on top of the toilet tank. See above.
3. The remnants of a roll of toilet paper sitting on top of a fresh roll of toilet paper on the tp holder. See above.
4. Your own image partly visible in a mirror as you take the picture.