A suggestion.
Exactly what the subject says: being able to rate half stars. That way you can rate something like 4.5 stars or something. Alternatively, a 10 star rating system would work just as well. Because if you do the math, right now, if you don't think a map is perfect, but still good, you can only give it four stars, which totals to 80%. But what if you're kind of stuck in the middle with a map? It's not good enough for 100%, but too good for 80%? Just talking about adding more options here.