Many haunts end with a chainsaw....to many. so thinking along those lines though and along your theme....
1. A scene where the deranged farmer puts people into a bailer and makes them into hay bails square corpses wired like hay bails?
2. A wood chipper scene? he is feeding parts into the woodchipper and then turns on the group?
3. The hog pen- (Ok this will sound odd but will be scary) Two fat men (or more) wearing only diapers and pig masks calling sueey! charging the group with lines like "Its Bacon!!!" Use actor power to get them running out of the doors.
4. Perhaps a stilt monster for the end, Pumpkinhead, a werewolf, a scarecrow, or a half cyborg/half tractor robot monster.
5. a sparkwand attached to the cycle you mentioned as the farmer attacks the group could be cool
6. FrankenCow- yup a farm version of Frankenstien's lab but with a monster man cow on the table, of course he gets up and attacks the group
Thats all that immediately pop into my mind hopefully you will get more from a few others.