The (python) script below creates sub folders and organizes your files into the folders:

Additionally:

• The script calculates the number of folders and adds leading zeros to the folder names for proper sorting (since you mentioned thousands of files, meaning hundreds of folders)
• The number of files per folder may vary, depending on your setting in the head of the script

The script assumes:

• All files have an extension, all files have the same extension
• Your files are named image1.tiff, image2.tiff etc (no leading zeros).

The script

#!/usr/bin/env python3
import os
import math
import shutil
#---
directory = "/path/to/files"      # path to your files
n_perfolder = 7                   # number of files per sub folder
#--
# creating file list, extension
f_list = os.listdir(directory); ext = f_list[0].split(".")[-1]
# calculate number of folders
n_folders = math.ceil(len(f_list)/n_perfolder)
# creating folder names, including leading zeros
folders = [str(fn+1) for fn in range(n_folders)]
fl_names = [(len(max(folders, key=len))-len(fl))*"0"+fl for fl in folders]
# creating folders and allocate files 
for i in range(len(fl_names)):
    mkfolder = directory+"/"+fl_names[i]
    if not os.path.exists(mkfolder):
        os.makedirs(mkfolder)
        r = range(i*n_perfolder+1, i*n_perfolder+n_perfolder+1)
        for n in r:
            try:
                file = directory+"/"+"image"+str(n)+"."+ext
                target = mkfolder+"/"+"image"+str(n)+"."+ext
                shutil.copyfile(file, target)
            except FileNotFoundError:
                pass

How to use

Copy the script into an empty file, in the head section, set the directory to your files and the number of files per sub directory, save it as organize.py.

Run it by the command:

python3 /path/to/organize.py

Note

If you'd like to move the files instead of copying, replace the line:

shutil.copyfile(file, target)

by:

shutil.move(file, target)

(mind the indent!)

How to make a playlist from a directory of mp3 files?

cd to the directory and

ls -1 *.mp3 > playlist.m3u

It turns out that there exists a fairly universal format called m3u format, and it can be as simple as a list of filenames separated by newlines.

After my wife had moved the mp3 files she wanted onto an empty thumb drive, I opened a terminal, browsed to the media directory, and typed the following and hit enter:

ls -1 *.mp3 > playlist.m3u

I then opened the file for her in gedit and let her copy and paste the lines around as much as she wanted to get them into her desired order.

When she was done, she saved the file, double-clicked it in a folder browser, and RhythmBox opened it. She clicked play, and it played, and I was a hero.