Question Summary:
Is it Bid’ah to place a Musalla for the Mukabbir behind the Imam?

Question Detail:

 there s a person (responsable) in our mosque who keeps putting a musallah (prayer mat) behind the imam for the mukabbir when we try to tell him is not necessary he insist and keep putting it.
is this a form of bidah?
could this become a form of bibah?
should we stop him or let him do so?

Answer :

In the Name of Allah, the Most Gracious, the Most Merciful.
As-salāmu ‘alaykum wa-rahmatullāhi wa-barakātuh.
If the responsible person does not regard placing the Musalla for the Mukabbir as necessary and he does so for administrative purposes or out of respect for the Mukabbir, then that is not Bid’ah.
And Allah Ta’āla Knows Best
Bilal Ishaq (Issak)
Student Darul Iftaa
Leicester, England, UK 
Checked and Approved by,
Mufti Ebrahim Desai.