du can accept a list of files or directories from stdin (or sufficiently new versions can, anyway). So you can use find and friends to filter and provide this list:

find Pictures -mindepth 2 -type d ( -execdir test -f '{}/0k' ; -o -print0 ) |

  du --files0-from=- -h

• With -mindepth 2, find will only list directories (-type d) at least two levels deep (so Pictures/*/*)


• In each of these directories, find will run test -f "{}/0k", which simply tests for existence of a file named 0k. ({} will be replaced by find with the directory.)
  
  
  
  
  • If the test succeeds, nothing happens. If not, the directory path is printed with an ASCII NUL at the end (-o print0).
  
  
  • The way -o works, the execdir and -print0 need to be grouped using (, ).
  
  


• du will then take these directory names and happily provide disk usage.

Sorting:

find Pictures -mindepth 2 -type d ( -execdir test -f '{}/0k' ; -o -print0 ) |

  du --files0-from=- -h |

  sort -rh