did a quick google search & the negative would be having the garbage can, jumbo monitor, oil excavator, tire place equipment, picnic sheet, traffic light, illumination items, and tower. i think it sucks you get punished for certain pwps. ):
the things that "don't count" too negatively are things like the water well, fountain, clocks, signboards, face boards, signs, art, monuments, etc.
didn't see the instrument shelter on the good, ok, or bad, so i'm guess it's ok to have.
i have two on the bad list, but that didn't stop me from not having a perfect town. not sure what the limit is, though. read somewhere else that someone got a perfect town with the instrument shelter, if that's any reassurance.