Here they are finally finished:

Cloud Faerie
Small Fey
Hit Dice: 2d6 (7 hp)
Initiative: +1
Speed: 20 feet (4 squares)
Armor Class: 10
BAB/Grapple: +1/-5
Attack: Dagger+2 melee (1d3-1)
Full Attack: Dagger +2 melee (1d3-1)
Space/Reach: 5 ft./5 ft.
Special Attacks: Spell-like abilities
Special Qualities: Vulnerable to Cold, Low-light vision
Saves: Fort +0, Refl +3, Will+3
Abilities: Str 8, Dex 12, Con 10, Int 14, Wis 13, Cha 15
Skills: Balance+12, Jump+10, Knowledge (Planes) +11, Move Silently +12, Perform (Dance) +12, Tumble +12, Use Magic Devise +7
Feats: Acrobatic
Environment: Any Warm Atmosphere or Land
Organization: Solitary or group 2-6
Challenge Rating:
Treasure: Standard
Alignment: Any Good
Advancement: As per class
Level Adjustment: +1

A little girl, radiant and beautiful, shapely as a fairy and exquisitely dressed, was dancing gracefully in the middle of the lonely road, whirling slowly this way and that, her dainty feet twinkling in sprightly fashion. She was clad in flowing, fluffy robes of soft material like woven cobwebs, only it was colored in soft tintings of violet, rose, topaz, olive, azure, and white, mingled together most harmoniously in stripes which melted one into the other with soft blendings. Her hair was like spun gold and flowed around her in a cloud, no strand being fastened or confined by either pin or ornament or ribbon. Her eyes were violet and full of tears….

Cloud fairies are the fey attendants of the Rainbow King who lives in a cloud castle. Occasionally, they will slide down a rainbow to spend time in the land below. In order to return to the cloud castle, a cloud fairy must find and catch another rainbow for her return trip.

When a cloud fairy arrives on terra firma, she will frequently be surprised to find the land below to be chilly. As they live high in the atmosphere, they are used to the rays of the sun. A cloud fairy will dance to keep herself warm if she lacks proper attire.

Cloud faeries eat very little and mostly live on mist-cakes and dew. They speak Sylvan and Common.

Air Elemental Bloodline (Ex): Clouds fairies get a +2 bonus on Balance checks due to their connection to the elemental plane of Air.

Pass without a Trace (Su): Cloud fairies leave no tracks or markings upon the ground as if by a pass without trace spell and they receive a +2 enhancement bonus to move silently checks.

Spell-like Abilities (Sp): 3/day—color spray or fog cloud (DC 13), 1/day—gust of wind (DC 12).

Skills: Balance, Jump, Knowledge (Planes), Move Silently, Perform (Dance) and Tumble are class skills for cloud fairies.

My only problem is: what do they do that pixies can't?

Does look like a PC-quality race, though...always glad to see that.

Hmm, indeed, I wonder how these almost-Pixies will mix with the more customizable Fey racial stuff.

Maybe I shouldn't go too 'modular', and save such a concept for something else.

It does look PC-worthy but I also wonder if we should make more LA+0 races, and then allow PCs to just add levels on top of that.
The Fey racial abilities would then progress in minor ways at the same pace but parallel to class abilities (a small idea I've been considering with feats, but 4e apparently will have the same mechanic. argh... must beat them to it...)