I can go to "http://members.byond.com/member_files/c/o/" and anything branching off of it (like http://members.byond.com/member_files/c/o/Cowdude) (I only tested with /c/o/ but it may work with others)

Any of the parent directories (like http://members.byond.com/member_files/c/ or http://members.byond.com/member_files/) send you to the members.byond.com page though.

I just had gone to the Properties of my blog icon to see what the icon's size was (because its evil and resized it so its stretched) :( Then since I was bored and had given up changing my CSS again I decided to try going to the directory its in even though I assumed I'd get a 403 error but I was bored :)

This seems to be just the directory you hold blog pics and stuff in, but I dunno if you'd want it blocked off if you ever use it for something else.