In Isaiah's Vision in the Temple of the Lord seated on His Throne, he saw a heavenly order of beings that he called the 'Seraphim.'
They had 6 wings, like John's living creatures and cried 'Holy, Holy, Holy, is the Lord of Hosts: the whole earth is full of His Glory' in Isaiah 6:1-4, but they stood above the Throne, while Ezekiel's Cherubim supported the Throne, and John's were in the midst or around the Throne.