First, excuse me if my english is extremely limited

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All the discussion about being or not being too alien is a bit relative. Every race in Mass Effect (except rachni and hanar,) are bipeds extremely close to humans. If I have to think in real aliens I actually cant imagine an Asari or Turian in real life (even a standard "grey" sounds a bit ridiculous), so, knowing that, we have to think in aliens in a science fiction context, and then, every possible "artistic license" is allowed xD (I never saw anyone complaining about alien races in star trek being too human!).
I can actually imagine a race of aliens who by nature has short hair (because it only grows 3-5cm in total), so no haircut needed

. I think it is more important to find a design of an alien race you like and think it fits, than searching a deep scientific sense to that look.