I don't think I'd go so far as to call it a pet peeve, but I like to see some thought into stuff in / on a vehicle. If a tool is mounted on the side, it should actually be mounted, not just glued on. If there is stuff in the back of a pickup / station wagon it should look like a load someone would put in the back, not just stuff randomly sprinkled around (real stuff slides around, so you think about how you place it if you are the driver).
I'm not big on engine detailing, but yeah, the floating alternator bugs me ever since it was mentioned in that other thread.