Garuda / Karura / Tengu are all pretty much the same thing : Body of a man, head of a bird, withs of a bird. Sometime depicted with head of a man instead of a bird.
Kinnara differ from Harpies though, they sound more like your Icharii. Kinnara are the upper body of a woman and the lower body of a swan, sort of minotaur-ish.
Harpies are more like complete birds with a human head (and sometimes breasts). They unlike the Kinnara don't generally get depicted with arms. Harpies are more like Alkonost
We can use the names of these mythological creatures and change things about. We can also use different birds as the basis for the bird section. For example a swan, hummingbird, crow, vulture and golden eagle are all very different birds.
http://www.environment.gov.au/biodivers ... light.html
An example might be
T1: Kinnara Icharii - Lower body of a swan, upper body and head of a humanoid, wings of a swan (rapid take-off)
T2: Karura Icharii - Full body of a humanoid, head of an albatross, wings of an albatross (gliding)
T3: Garuda Icharii - Full body of a humanoid, head of a humanoid, wings of a swallow (speed)
T4: Tengu Icharii - Full body of a humanoid, head of an eagle, wings of an eagle (soaring)
T5: Harpy Icharii - Body of an over-sized robin, upper-chest and head of a humanoid, wings of a robin (quick manoeuvres)
What's more important is the general idea behind the Icharii, which only you and the people that have roleplayed the race can decide. In the end, it might be my call in what racial troop names we use, but in canonising a player-created race, then it's not down to me to change the idea of the race itself.
Having the body and head of a humanoid with just the wings of a bird, already diverts from standard mythological creatures except for angels (I'd rather not use angels as a species/troop type). If Icharii had body of a humanoid, head of a bird (with the ability to shape-shift the head) then you could literally just differentiate by bird type, which would be simpler, but I don't know how well that would agree with the roleplay of the race itself. Another alternative would be a humanoid/avian shapeshifter who can shift between humanoid and avian form, or chose to be somewhere between the two.
I'll help expand with ideas, but in the end I'd rather see an Icharii race come out of the people that roleplayed one, not just enforce one.