There are requirements for phpBB here:
Specifically, item 4 under Quick Install:
Change the permissions on the following directories to be writable by all (777 or -rwxrwxrwx within your FTP Client):
store/, cache/, files/ and images/avatars/upload/
On this forum, I saw:
It gets a little over my head with the code, but at the heart of it, it seems there’s a problem with some kind of avatar related display functionality or hosting of images (I couldn’t actually tell which was the issue), and that the issue has not yet been resolved, or had some kind of very difficult fix that I might not be able to figure out within the next year because I have no exposure to code.
Is this something I’m going to have to worry about?