Answer:
All perfect praise be to Allah, The Lord of The Worlds, and may His peace and blessings be upon our Prophet Mohammad and upon all His family and companions.It isn`t permissible to finance decorations for stores through Murabaha since this sale/transaction is about existing commodities which are purchased and received by the merchant, then sold to the customer. However, since decoration works in this case are non-existent commodities, Murabaha sale/transaction isn`t valid. Rather, these decorations take the ruling of non-existent commodities, and financing them is considered a forbidden loan because it involves usury{Riba}.
The alternative is that the customer concludes an Istisnaa` contract (Making on customer`s order) with the financing institution to have the decorations of his store made, because this contract is about the commodities to be manufactured and are non-existent at the time this contract is concluded. And Allah knows best.