query: SELECT ?item ?itemLabel ?count WHERE {
  {SELECT ?item ?name (COUNT(DISTINCT ?creator) AS ?count) WHERE {
    ?painting wdt:P31 wd:Q3305213 .
    ?painting wdt:P195 ?item .
    ?painting wdt:P170 ?creator . 
    } GROUP BY ?item ?name
  } SERVICE wikibase:label {
      bd:serviceParam wikibase:language "en" .
    }
  } ORDER BY DESC(?count)
  LIMIT 200