Throw anything Feat + Tower Shield

[AshleyShields]

So I've got a player who wants to use a tower shield with the "throw anything" feat. I have no problems with the throwing of it, however, the discussion we're currently working on is how much damage will a thrown tower shield do? I've had a couple people point out the improvised weapon rule that we should find the closest equivalent in the weapons table and then use that damage dice. Honestly, we can't find anything close to a 45 pound weapon (that's the weight of the shield). I'd love to have some feedback and possible get a consensus of what the shield will do.

Things we've figured out:
shield weighs 45 lbs.
will do bludgeoning damage + strength
character will need proficient strength to do this
range of thrown shield is only 10 feet

[Jericho Graves]

I would just call it greatclub damage and call it a day. But I've been called fast and loose before.

[Doomed Hero]

A Tower Shield is about the size of a heavy shield for a Huge creature.

Figure out the damage of a huge creature's shield bash and use that. (It should be about the same a great club if my memory of damage dice increases is right)