You confuse me

"ranks" as you call them are given based on posts, exactly the same as the avatars. You can create the avatar folders to match your user titles. The avatars that you downloaded may have created directorys 0,1,10, etc but you by no means have to use them. You only have to have a 0 directory and then you create the rest based on what you want to give for whatever amount of posts.

ex.

0 - 19 none - (Create a 0 folder and put 1 image in it)
20 - 99 junior member (Create a 20 folder and put 25 avatars in it)
100 - 399 senior member (Create a 100 folder and put 25 avatars in it)

and so on..