I really doubt that mural is enough to insinuate on the race/gender of the hero. It's a generalised player. It's man/mer. Probably the most common played character. It needed to be represented by something.
Anyhoo, here's my theory:
Alduin, the Nordic envision of Akatosh, who destroys the world, uses dragons (they represent Akatosh) to destroy everything. He keeps them far beneath the ground for when he needs them next. The Oblivion crisis woke some of them, and they're now trying to destroy the world/gather more dragons. The player has to unite the clans of Skyrim (probably requiring you to fulfill some prophecy) to battle against the summoned armies of Akatosh. Battle takes place, and you need to go in, slay the dragons, perhaps with some special method (ala stabbing Lorkhans heart), and everyone lives happily ever after. Obviously, WAY more in detail.
The minions aren't actually under Akatsh's control. They where awoken at the wrong time, and Akatosh is mega weak after his brush in with Dagon, and hasn't the power to stop them.
I know this sounds a lot like Morrowind's plot, but, look at the games. They are very similar. I mean:
- Morrowind - Find Caius Oblivion - Find Jaufree
- Morrowind - Do some quests for Caius Oblivion - Save Kvatch
- Morrowind - Fulfill prophecies Oblivion - Get Martin's items and get the "army"
- Morrowind - Battle with Dagoth Ur Oblivion - fight through the great gate
- Morrowind - Stab the Heart Oblivion - take the sigil stone
Just a very basic overview, incase anyone tries to diss my theory.
Oh, and I doubt we'll be the "sidekick" again. It was one of Oblivion's big complaints.