Some tiny changing to user.php?

Hello, I'm new here. I've started learning PHP since 1 week ago. I now know the basics of PHP. But anyway, I don't know enough PHP to do the following:

When you try to change an user's avatar from the Control Panel, you'll see a list of avatars. That's normal, but this is what I want to do:

As the server where my board is hosted doesn't allow writing on the disk (I've tried everything to get the uploads to work, but it's no use), so I've been thinking of a way to get custom avatars, so I've created an apart page (in PHP), which lets an user e-mail me with his/her avatar, so that I'll upload it by myself (using FTP), and link it from the images/avatars/custom folder. But since in the CP all avatars are displayed, it's pretty hard to see which ones the uploaded are... So, I'd like that somebody could give me the correct code to seperate the uploaded files in the custom folder from the original avatars (in the database), so that it's easy to select them.

PS: I've placed that avatar at the highest post count: 12676 (or something), so that none of the users can use the avatars, except the admins in the CP.

Edit:

Never mind about that. Since I don't get any help, which was really too bad, I've tried it again and looked at the codes/variables very carefully and managed to do it.