Done Does anyone know what デコ is...?

[Olivine]

Just as it says above. And no, it is not short for デコレーション, or decoration.
It's used in this context; "おぬしデコじゃのーう。デコデコじゃのーう。"
(Yes, I know that sounds a bit creepy, but that's what it is.) And that is some strange dialect for "You are デコ. You are デコデコ."
I searched, my best guess for what デコ is was some sort of hairstyle that shows the forehead. (Like おでこ.)
So I guessed it was; "You show your forehead. You show a lot of your forehead." But I'm pretty sure that's not right.
So...does anyone know what デコ is, and what it should be translated as...?

 

[cmertb]

More likely it's a sort of an insult for someone who has a big forehead.

 

[Olivine]

Oh, that makes sense. Now how do I change this into [solved]...Here we go.

 

[noona]

Or it may mean 'protruding', as in the デコfrom凸凹（でこぽこ）, which can also be used to describe a protruding forehead, according to the context you provided.