Class Profile Picture

[Niwashi]

For the forum profile picture, go to Settings and under the "My Settings" block, choose "Edit Character". This will let you choose which of your characters and which of their classes you want to show up as your avatar. (What level that class is at and what you're wearing is the part that will be updated whenever it is that the lodestone pulls data from the game servers.)

It's also the character and class you choose here that determines your posting privileges. (Those with higher level avatar characters get to post more often.) That's why I now have Dylise as my avatar even though I regard Y'kayah as my main character.

As for the Lodestone: when logged into the Lodestone, at the top right corner of the "Character Profile" box is an "Active Character Settings" button. Click that and it will let you switch which of your characters you're logged in with, but I think the class shown is whichever you logged out as.