The whole tons of races look like humans except for the head irks me in general. We're supposed to believe that on each of the respective home planets of these species that their evolution was directed by occurrences that lead to a perfectly human looking body (same number of digits, proportions, etc.) but something happened in their environment that made everything from the neck up (or in Zabrak case the forehead up) be radically different..... Sure there are some races that have a radically different body in the Star Wars universe but you don't see multiple races with say a body like a hutt but with tentacles for hair.
That's because they are Near-Humans
: almost all are evolved from a human ancestor, adapted to some random condition of their planet.
It's silly, but that's what happens when you base an entire mythos on a movie from the 1970's.
Alternatively, consider convergent evolution
, the perfect handwavium for explaining humanoid aliens.