Well, if he does not navigate around Africa, he can use his fleet to seize Cyprus and secure the island and the Levant, including Syria, giving him a big revenue, because now he can control all the commercial routes, and use it as a base to capture Anatolia.
Also, his father Nabopolassar was very old at the time he took Ninive, in fact he died just after the battle in OTL. If Nebuchadnezzar died in Carchemish, that would be a fatal blow to Babylon.
Looking all the previous ATL around the same age, i can think in some kind of military reform, inspired in the nomad tribes just at north of Syria, and the greek mercenaries (Necho after the defeat started relationships with carians and greeks), in order to start to conquest all the surrounging states.
And yes, the biggest impact would be cultural, just imagine, egyptian temples in Anatolia and Babylon...