It may sound an odd complaint to make about a sci-fi series, but does anybody else think there's too many aliens on Star Trek? particularly ill thought-out ones.
Voyager is the worst offender in this respect, that's one reason I couldn't bring myself to keep on watching it. There's new so-called "aliens" every week and they're basically just humans with odd bits stuck on to their faces. Or even completely human-looking with not even the slightest token indication of anatomical differences.
I know the basic restraint is the fact that you've only got human-shaped actors to play these characters. For precisecly that reason I would have cut down on the number of aliens. Or at least have some real CGI oddities that could be any shape the programmer decides. For the humanoid races, I doubt they'd be spread all over the universe in any case, and I'd be quite happy to stick with a few reasonably differentiated races that have been established. You can believe that something like a Ferengi or a Klingon might exist and be a genuinely different race, but I'm having trouble with the vast selection of blatant humans with slikghtly differing bits and ends glued to their faces.