I have several aliases that I was unable to choose an avatar for when I created them because by the time I found one I wanted to use, I had timed out and my changes were saved. Now I cannot see any way to give these characters avatar images. Is this in fact the case or is there something that I'm missing?
Go to Your Account, select Edit next to the alias in question, then click Change next to Avatar Image.
EDIT: Oh, wait, you said PFS character. Go to Your Account, scroll down to Pathfinder Society, click Make Changes, click Edit next to the character in question, then click Change next to Character Image.
That's the thing - there's no Character Image for there to be a Change button next to.
edit: nm. I figured out what you were saying. For whatever reason, going to the profile view from the alias list doesn't give the same options as the character list in the my account screen.