I recently needed to batch delete all of the files in my filepicker.io account, but there is no way to do that through their UI or APIs, at least that I could find (unless you still have all their IDs in your own database in which this is not necessary). In their Developer Console I can browse the files in the account and delete each one individually, but that would take an extremely long time for hundreds or thousands of files.
My solution is still a bit slow and manual, but much much faster than clicking each one individually. This is a simple javascript snippet that can be run in your browser developer console on the Browse Files page when logged into Filepicker.io
$('.filelink').each(function(index){
var url = window.location+'/remove/';
var handle = $(this).attr('data-handle');
$.post(url,{handle: handle}, function(response){
console.log(handle);