An example of a bad one might be a cell phone tower. I am sure no body keeps any pics of those.
I actually once lost out on a job because I couldn't come up with a perfect routing that avoided looking at a cell phone tower in one corner of the property. The client was just obsessed by it! But he never built the course, anyway.
There are tons of off-course objects that are used as focal points on good and great courses. On the newer course at Stonewall, there was an old church just off one corner of the property, which we managed to get two holes aimed right at. The client even gave them some money [at my suggestion] to re-paint the church so it would stand out more.
On-course objects are much more rare, but I have a whole list of them in the back of The Confidential Guide. Some highlights:
the stone wall at North Berwick
the church which is in play on the 4th hole at West Cornwall, Eng.
the lighthouse at Pacific Grove, Turnberry, Old Head, and Royal Cromer [we're supposed to build one for our island project in China]
the castle ruin at Pennard
the round tower on the 3rd at Tralee
the farm windmill on the 1st at Sand Hills (or did they take that down? They debated it endlessly. Dismal River has another which you could actually HIT with the second shot on a par five; I thought that was crazy.)