Pretty much anything can be used as fixed capital, provided it is used by the entrepreneur/firm to provide a service or produce something valuable. If the firm is a hotel, then pillows and vacuum cleaners are fixed capital; if it's a store, then the cash register, the shelves, and the mop are fixed capital.
Another form of business capital is circulating capital. This is called capital because it's a physical object used to produce value, but its purpose is to be sold or used up in production.
Adam Smith, *The Wealth of Nations* (1776)