Here is a pic.   

Here is another. 

Can you see if there's any discoloration on the under side of the back-plate as-well ? Key is to see if they correspond to the same positions as the 
discolorations on the PCB. I've also noticed they have notched out the back-plate above certain components. Might be a little difficult to match them.

I will check, I think the one where the gpu does but I will have to turn off my pc and get the back plate off again, i will get back to you in a few minutes, thank you for being so helpful. :)

Oh my bad, just realized it was back in your PC lol. Take your time, but this information can be invaluable to this community, as-well as maybe yourself.

I do not see any scorch marks but I see more discolored spots, I will take another picture.

Here is another picture.

Here is one more.

RKarov
Here is one more.

That is nothing to worry about. Oil residue from thermal pads isn't a problem.
 
You can see the pads here...
 

 
 

This is from the back of the board not the front where the GPU is.  Going to sleep. 4AM here will get back to this later.