query: SELECT ?item (SHA512(CONCAT(str(?item),str(RAND()))) as ?random)  WHERE {
    ?item wdt:P195 ?museum.
    ?museum wdt:P17 wd:Q31.
    ?item wdt:P18 ?image.
    MINUS { ?item wdt:P180 ?depicts }
  } ORDER BY ?random
  LIMIT 50