Hey Wildcard. Are you a console player? Unfortunately, only players who have purchased the game on PC can post in the General Discussion forum. If you have purchased the game on PC, make sure you’re logged in to the same account you used to purchase D3.
As for not being able to post pictures, that’s a feature of the forum trust system. You can read more about it here:
There’s also a way for players who don’t yet have trust level 3 to work around it (cheers Perusoe!)