what would be unusual about your observations of occupants in a space ship traveling at reletivistic speeds?

Assume you can cleary see them make any measurements you like.

They would be compressed horizontally and move very slow. The extend would depend on how fast they are going

The answer above is correct as long as you are clear what you mean by "move slow". That doesn't mean the spaceship is moving any slower. Everybody agrees how fast the spaceship is going. But the people inside will be slower (in every way) because their time is slowed down. If the trip is long enough, you will see that they live longer than a normal human lifetime.

Of course the other "unusual" thing you may notice is their spacecraft getting buffeted by a fierce apparent wind of cosmic radiation boosted to high energy by their relativistic speed. Unless they have some great method of shielding and heat-dissipation, they will be cooked.