The generic D&D feel comes from the four core classes - fighter, mage, cleric, thief. However, swapping those out for others can change the feel of a campaign from the very beginning, as it alters the assumptions and expectations of the group.
Example: the Ancient Races Core Campaign - core classes: Vaultguard, Craftpriest, Spellsword, Nightblade
This is an all dwarf/elf campaign, so it would probably involve ancient relics and protecting wilderness areas from humanoids. This one uses only classes from the core rulebook; adding the PC, there could be all-dwarf or all-elf campaigns.
Example: the Chaotic Campaign - core classes: Ruinguard, Assassin, Witch, Warlock
This campaign could either be centered around Zaharan ruins or the corruption of the Empire.
Example: the Holy Campaign - core classes: Paladin, Cleric, Bladedancer, Priestess
Possibly less combat-oriented, this would likely look at countering the corruption in the Empire
Example: the Wilderness campaign - core classes: Barbarian, Explorer, Shaman, Ranger
All classes that do well in the wilds.
Example: the Court campaign - core classes: Bard, Courtier, Machinist, Venturer
Classes that one could see working for a noble in their court.
What other themed campaigns can we come up with?