Some of the old battleship and battlecruiser names from WW I probably would have been used. Though Hindenburg, Ludendorff, Moltke, Fredreich der Grosse are four names I can think of off the bat. The type O BCs would have been named differently, the carriers after famous aviation pioneers (Graf Zeppelin as the lead ship, Peter Strasser was the reported name of the second of the class, while the liners that were considered for carrier conversion were to have kept their original names (Europa, Potsdam). Light cruisers would have maintained the tradition of city names, while the Heavies would have got the names of famous generals, admrials, or princes. Destroyers would simply have had a Z-number.