Creatures From Outer Space!!
The above sketches are for a creature called a "Ymir" a lifeform from the planet Venus used in the black and white monster on a rampage movie "20 MILLION MILES TO EARTH." Additional artwork of the alien can be found here.
You can see the creature kicking ass in a barn here.
The above 2 sketches were made for the classic science fiction film "Earth Vs The Flying Saucers." And although these drawings show the potential of some very bizarre stop motion creature scenes, all attention in the animation department was put towards the alien saucers. This resulted in some of the most incredible scenes of science fiction cinema.
In the film "First Men In The Moon" Ray brought to life giant caterpillars also known as the "Moon Cows" and the smaller insect like creatures that dwelled under the moon's surface. Although a few of the alien characters from this bug like race were animated, most of them were made up of children in alien costumes.
Last we have what could have been Harryhausen's best foray into creatures from space, "War Of The Worlds." Unfortunately this never worked out and we are only left with these sketches and this test animation of an alien exiting a ship.