Why some background parts are low resolution?

[Mazisky]

The Backgrounds are beautiful and most of them are really well rendered.

 

I noticed tho, that some parts are low res and contrast with the rest, why?  Is there a chance to see those parts hi-res like every other places?

 

 

Example: Gilded Vale Temple (the stairs at the entrance, the bells)

 

Another example: the cave with the red Dragon (the "lava\stone" background)