Characters that join the Ebonheart Pact will, if they make certain choices, have the chance to run into Joruun the Skaald-King and other prominent figures like the Nord Companions. All members of the Ebonheart Pact will have a chance to visit the Shadowfen and the Argonian city of Stormhold, which likely means running into the huge, reptilian wamasu that lurk in the swamps.
The Great House rivalries that players came to love in Morrowind will figure into TESO, although players won't (initially, at least) be able to formally join a House. Similarly, players who loved Skyrim will find that while the land is familiar, it's got substantial differences as a result of being about 1,000 years younger.
Argonian players who're fond of the extremely reptilian look will be pleased to hear that character customization will allow for "much more variety than [the team has] been able to convey in the screenshots released so far." To read the full answers, hit up the official Q&A.