Well, there really isn't a single link to download 'the best art'. But you can list all the art in order of most likes, then download them in that order.

http://opengameart.org/art-search-advanced?keys=&field_art_type_tid%5B%5D=9&field_art_type_tid%5B%5D=10&field_art_type_tid%5B%5D=7273&field_art_type_tid%5B%5D=14&field_art_type_tid%5B%5D=12&field_art_type_tid%5B%5D=13&field_art_type_tid%5B%5D=11&field_art_licenses_tid%5B%5D=2&field_art_licenses_tid%5B%5D=3&field_art_licenses_tid%5B%5D=6&field_art_licenses_tid%5B%5D=5&field_art_licenses_tid%5B%5D=10310&field_art_licenses_tid%5B%5D=4&field_art_licenses_tid%5B%5D=8&field_art_licenses_tid%5B%5D=7&field_art_tags_tid_op=and&field_art_tags_tid=&name=&sort_by=count&sort_order=DESC&items_per_page=24&Collection=