Genasi should be as varied as any other kind of planetouched. An earth genasi might have the blood of some spirit of soft soil or ooze, or some kind of brittle crystalline elemental. Or they might have skin as tough and shiny as steel. An air genasi might have all the might of a hurricane, or be as delicate as a sprite. All attempts to generalize them will fall short.

Cribbing ideas from the Nephilim game:

Kranach (fire genasi) - flaming hair, claws like a bear, steaming skin. A crackling voice, harsh as a whip. The odor of burning. Ability adjustments: +2 Str, -2 Cha, -2 Wis. Favored class: fighter.

Ambalatee (fire genasi) - Red pupils, irises, "whites," joints, ears, lips, and gums. A growling, choleric voice, sounding close to the bellowing of tigers and lions. Black talons. The odor of sulphur. Ability adjustments: +2 Cha, + 2 Wis, -2 Str. Favored class: paladin.

Aeolus (air genasi) - Blue on blue eyes, cold hands, transluscent skin. Smells of ozone. A voice loud and low, rolling like thunder. Claustrophobic, messy. Hyperactive, noisy, absent-minded. Ability adjustments: +2 Dex, -2 Wis, -2 Cha. Favored class: rogue.

Zestumago (air genasi) - silvery, heel-length hair; long, thin fingers; cloud-white skin with silvery undertones; feathers instead of body hair. Smells of springtime and flowers. Attracts bees. Musical, melodious voice. Gentle, curious. Ability adjustments: +2 Int, -2 Con. Favored class: wizard.

Bogo (air genasi) - Black skin, simian features. Leathery, webbed arms. Colorful garments that shift and change. A gravelly, ever-changing voice. The smell and feel of morning dew. Ability adjustments: +2 Cha, +2 Int, -2 Wis, -2 Con. Favored class: bard.

Bahaflass (water genasi) - Jagged ears, thickly webbed hands. Blue, scaly skin; pointed teeth. Eyes like spiralling vortices. Smells of plants and swamp gas. Voice eery, low-pitched, toneless and harsh. Ability scores: -2 Int, -2 Cha, +2 Str. Favored class: barbarian.

Manala (water genasi) - thin, straight hair. Finely webbed hands and feet. Smooth, undulating skin with layer of fat. Smells of salt. Liquid voice accenting the 'L's. Ability scores: +2 Dex, -2 Str. Favored class: bard.

Ghruuul (earth genasi) - warm, pebbly hide; long arms; glowing orange eyes; small tusks; bald, with a bony crest. Ability scores: +2 Con, -2 Cha. Favored class: fighter.

Mantichora (earth genasi) - leonine mane; coal-black eyes; metallic teeth. Thick, three-fingered hands. Surrounded by cloud of dust. Deep bass voice with rolling 'R's. Ability scores: +2 Cha, +2 Wis, -2 Str. Favored class: cleric.

Gobblyn (earth genasi) - Transparent, slimy skin. Small, thin body. Spidery arms and legs, clawlike nails. Pointed ears. Smells of rot and filth. Shrieking voice like chalk across slate. Ability scores: -4 Cha, +2 Dex. Favored class: rogue.

Yvintuel (earth genasi): Greenish-gray skin, with grainy textures. Black oily hair; pointed ears. The smell of damp soil. Fast speech, deleting his vowels. Active, healthy. Withdrawn and brooding. Confident and calm. Ability scores: +2 Wis, +2 Con, -2 Int, -2 Str. Favored class: druid.

Let me reiterate that most of those ideas are stolen from Chaosium's Nephilim RPG (except Bogo, whose dad was a Spirit of the Air - originally I wanted to base him on a "Nephilim" harpy, but the result would have been another rogue, and there's no point in that). Anyway, the Planewalker's Handbook specifically mentions that some air genasi are spawned by Spirits of the Air, so that was a hole to fill. Genies tend to be pretty fleshy, by the way, so it seems like the genasi descended from them wouldn't look like or have the same abilities as "typical" genasi either.

The half-elementals created by Monte Cook for Return to the Temple of Elemental Evil and reprinted in the new Manual of the Planes seem to be an attempt to create the beings from which standard genasi are derived. Half-elementals are to genasi as half-celestials are to aasimar. They look the same, but they're a bit more powerful, with a wider variety of supernatural abilities. Each of the four types has a different favored class, too. Half-elementals would make another good base to make genasi with alternate talents from.

Genasi in the Planewalker's Handbook have charisma penalties (and reaction penalties piled on top of that) because they're supposed to be all alien, inscrutible, arrogant, and convinced of their own superiority over all non-elemental forms of life. Half-elementals don't have this problem, though, so that's a justification to drop it from genasi. At least sometimes.

Unless genasi are going to get the extra feat and skill points a human gets, they should probably have special abilities. The ones in the PW's Handbook are a good start. It shouldn't be hard to think of others - some interesting ones could come from obscure elemental spells. I'd like to - coming up with variant genasi is fun.

There's something to be said for giving them a higher ECL. Creatures with nicknames like Wind Dukes, Earth Princes, Wave Kings, and Flame Lords should be more potent than humans of the same level. Well, they don't have to be - it could be all bluster - but they probably are. And they're so damn cool that I would play a genasi even if I had to give up a level for it.