When you get to the last room of Frossel Cave you see two rows of Rieklings worshiping a cart being pulled by a crudely made statue of a horse. Is there anything more to this than just a silly little scene? Can you become God of the Rieklings?

I tried sneaking down there with an invisibility potion and then suddenly appearing before them to see if they would treat me as an apparition of their god. But all they did is attack me.

Anybody found a way to get some alternate behaviour out of them besides instantly going agro?

They attacked Verena and Argis as soon as they saw them. I do not think you can tame them.

You can by doing a certain quest (for riekling followers) Or atleast it allows for a riekling follower. As becoming their god it states in a loading screen that they will find various trinkets which they will then grow a attachment to them, e.g you will find lots of gems and gold on little pedastals, they worship these.

As Jemofend basically said, Rieklings are the sort of grow attachments to and potentially worship objects that they scavenge.

The (remarkably intact) cart is an example of that.

Errr... that's not a statue. That's a frozen horse.

Take a closer look. I thought it was a frozen horse at first, but its not. Look in the center where a saddle would be. Also notice all the other oddiments tacked on to the base ice form to make it look like a horse.

I'm almost certain the Rieklings worship Karstaag as their god. I may be mistaken but this is what is inferred by the game. Any thoughts?

It's possible that they worship PARTS of him. Like, they worship his skull because it's an item they scavenged, etc.
Nothing to do with Karstaag himself, just that they found him and his throne and thought "Mine. Worship."

Speaking of the horse, Verena went to examine it more closely, (just in case there was good stuff up there to loot) and did anyone else fall out of their chair and roll on the floor laughing when they spotted the pieces of charcoal on the ground under the horses tail? I did and almost choked on my beverage. They tried their best to make the horse look realistic, bahahaha.

http://en.wikipedia.org/wiki/Cargo_cult

they worship cart horses because they are full of cool stuff, but for some reson they stick to using crappy home made spears, when they have some really good weapons in there loot.