Using 2 different AIM accounts, my Adium login can see the icon for my iChat login, but not the other way around.
On iChat (and apparently for all of my friends), all that shows is the generic "little yellow guy"
I don't think this is a firewall issue, since it happens both at home and at my office.
I tried to search for other threads, but both AIM and icon are excluded as "too common."
This has happened as far back as I can remember.
I have tried deleting and re-adding the account in Adium, and the same custom picture will show properly for MSN.