Guys, there is an even easier way. No need for all that fuss - it's just confusing.
Here's how to do it:
1. You need this software.
here.
2. Then, create a folder within the graphics/face pack folder, and call it, for example, Dundee FC Face Packs.
3. Then, gather all the players images you want - put them in this folder together.
4. Now, go to FM preferences, and click on Display & Sound, then tick the "show players unique ID" tab.
5. Now, if you click on any player on the game, it will show a unique ID number below their name at the top of the screen. Use this ID number to rename all your images of the players that you have found, and are in your graphics/face pack/Dundee FC Face Packs folder.
6. So, we now have all the players renamed as their unique ID number.
7. Now, open up the program I asked you to download.
It will look like this:
You will type in the route of the Dundee FC Face Pack Folder with all the players in it.
8. Make sure, "All filenames are ID's" is ticked, then click on "GO".
9. This creates a config folder for FM to understand.
10. Go to FM, click on preferences, untick skinn cache and click the one below.
11. Hey presto, that it's done.
Any problems, let me know.