You have to get some hosting, free or otherwise. I don't ahve a random avatar, but I do have my own hosting and I am--or will soon be--using this same script for something on my site. Try freewebs, it's crap but it works.
um i tried the random avatar thing i worked the first time i used it but now i found some pictures that got a little bit messed up and now none of my avatars will show.
Also when i try to delete my folder and try again the folder can't be deleted i used my ftp account to test is out now i have 2 of my folders and it says i can't delete this cause i don't have permission??
it shouldn't matter if you use the ftp or not, since avatar pictures are really, really small. i mean, mine has 160 pictures (and growing!), and is only 1.33 mb, which is next to nothing.
now, nothing i say is official of course, but there should be no problems.