Using Drupal 7.56 and Civi 4.7.28, our CiviMail's KCFinder 3.12 image browser has now more or less stopped working. There are about 700 images in the root folder, which is presumably the problem - many of our users are on less than high speed internet and the problem has been slowly getting worse as the number of images has increased.
The images are generally being used by other functions in Civi, so we can't easily change their path without a lot of manual work or an SQL query that would be beyond us.
What options do I have to improve things? NB: I just checked and indeed the system uses KCFinder, rather than CKFinder.