Given the size of the fleets (747, 777, Airbus) it would be difficult to find themes with sufficient names, unless they revisited rivers, castles, etc. <yawn>
The LCY-JFK 318s are a pretty small group though. Maybe something to do with babies ?
How about naming some of the flagship routes like the railways used to ? e.g. Flying Scotsman, Master Cutler. Which routes though ? My warped mind associates JFK-LHR with nylon ...