I'm not sure what they are exactly, I was hoping to find out through your answers.

Here are some songs that in my mind could reasonably be called 'centrepieces' of their respective albums:

November Rain
Paranoid Android (only track 2! Thinking out the box)
The Past Is A Grotesque Animal (Hissing Fauna)
All Around The World (Be Here Now)
French Lessons (How To Stop Your Brain... )

Centrepieces.