What does Marley look like?

Being a ghost, he would be rather pale. He also has chains around him. Other than that he looks basically the same as when Scrooge knew him,

The same face: the very same. Marley in his pigtail, usual waistcoat, tights and boots; the tassels on the latter bristling, like his pigtail, and his coat-skirts, and the hair upon his head. The chain he drew was clasped about his middle. It was long, and wound about him like a tail; and it was made (for Scrooge observed it closely) of cash-boxes, keys, padlocks, ledgers, deeds, and heavy purses wrought in steel.