Aliens aren't always reported as the grey, large-eyed, small-bodied beings as the one in the photo above. A wide variety of them have been reported by a wide swath of witnesses. I will discuss some of the more popularly described ones:
Reported with typical Aryan traits, they have blond hair, blue eyes, strong and robust, webbed toes, and 24 teeth supposedly. These are described as kind of like "star child" earth-loving, eco-weenie, peaceful sort of beings. A popularly held belief is that during Eisenhower's time in office, the Nordics arrived in a meeting in California with the president hoping to make a connection, but was rejected. Then, later, he met in New Mexico with the greys and made a deal with them instead - a deal they regretted later.
These humanoids are described as tall and scaly. Often, they are reported in caves or around caves. Encounters with reptilians have not always been positive and sometimes downright threatening, but they appear to want to remain very hidden and have also been associated with the ability to walk in and out of walls in a kind of parallel world membrane. Reptoids are often part of legends of cave dwelling and underground tunnels in the Ozarks and California.
Reported to have hairy bodies, small, almost alien grey shaped, but sometimes wearing a strange helmet on their head. These have so far been reported in Latin America.
The Sirians were said to be the first to visit our planet in ancient times, 4 to 5 billion years ago (how this is confirmed given there is no written language from back them of eye witnesses, I'm not sure). Reportedly, they along with other aliens, DNA manipulated our life on this planet.
Described as exceedingly tall, about 8 feet, with pale chalky skin and wrap around blue eyes. I saw two of these as a child (more on that on Wednesday). They are said to have translucent platinum hair. Iran believes there is a base of them under their land -
These beings are described as blue and said to have landed in Florida in the 1950s, trying to convince our government not to work with the greys to no avail. They have wrap-around eyes and are sensitive to light. It is said they are friends with the Nordics. From Exopaedia: "They claim to be descendants of Noah who traveled to the Western Hemisphere a few centuries after the deluge and discovered ancient antediluvian cavern systems and technologies which had been abandoned in the subterranean recesses. They have been encountered mostly in deep cavern-systems beneath the general region of the Ozarks-Arkansas and surrounding regions (Evadamic)." Other sources tell of encounters with this same race in the Southern States of the USA." As ludicrous as this sounds, much of the concept of underground caverns and alien civilizations really do ring true for most researchers who are finding more and more correlations, especially in the Missouri/Arkansas/Ozark area.
For more info on the variety of aliens, I suggest Alien Anthropology site.