The Caatati have suckers on all of their five fingers (VOY: "Day of Honor").
	We can make out small suckers on the thumbs of Tash's race too (VOY: "The Voyager Conspiracy").
	Dralians have suckers on their thumbs (VOY: "Critical Care").
	Finally we can see that Tamarians have something like suckers at the tips of their prolonged thumbs, but not on any of their other fingers that look human (TNG: "Darmok").

Openings Other aliens exhibit openings or pores on the backs of their hands, preferably above the knuckles.

	The barkeeper in the bar where Picard was allegedly shot has such a hand with openings above the knuckles (TNG: "Gambit I").
	Likewise, we can see such a hand make-up on the Botha (VOY: "Persistence of Vision").
	The old Cos exhibits these large pores as well (DS9: "Rivals").
	Furthermore we can see Trajis Lo-Tarik with such a hand. The make-up may be exactly the same as of Cos and of the Botha (VOY: "One").

Spikes Many species can be seen with spiky extensions on the backs of their hands. Here are just some examples.

	The Letheans can be seen with such hands in both of their appearances (DS9: "Distant Voices", "The Sword of Kahless").
	The Kressari are another example of a race with thorns on their hands (DS9: "The Circle").
	We can see the Nausicaans with such spiky hands too. Their pattern is different (ENT: "Canamar").
	Finally there is the "Dream Species" with yet another variant of spikes (VOY: "Waking Moments").

Varied backs There is a diversity of other modifications to the back of the hand.

	The Dopterians can be seen with oval structures on their hands that look like fingernails - or like thick white blebs (TNG: "Firstborn").
	Krit and Nahsk have hands with scales (DS9: "Who Mourns for Morn?").
	Flaxian hands exhibit streaks of hair, the same as in their beards (DS9: "Improbable Cause").

Long fingers Some aliens have considerably longer fingers than human beings.

	The trait of very long fingers can be seen on the Dremans like Sarjenka (TNG: Pen Pals").
	Marayna's race has very long fingers as well (VOY: "Alter Ego").
	One Bolian in "Star Trek: First Contact" has fingers that look unnaturally long. He seems to be the only Bolian with this trait. The fingers are never clearly visible in the very movie, the picture on the left is a scan from the Fact Files and probably shows a cut scene or a photo made at the set ("Star Trek: First Contact").

Other variations There are some more variations among the aliens with five fingers.

	A Zaldan bumps into Wesley and starts to insult the boy without reason, ostentatiously showing his webbed fingers. Wesley recognizes that it is a part of his Academy entrance exam. Knowing that Zaldans hate courtesy, he complains to the man about his bad manners (TNG: Coming of Age").
	Benzites have two thumbs and three other fingers (TNG: "Coming of Age", "A Matter of Honor").
	A Lauriento masseuse can be seen with hands that are coalesced to a lattice (DS9: "A Man Alone").
	Torat's race is without fingernails (VOY: "Counterpoint").

Fingernail colors Finally, while their hands look basically human, the fingernails of some alien species have distinct colors.

	Ferengi fingernails are bluish (TNG: "The Last Outpost" et al.).
	Orions have deep green fingernails (TOS: "Whom Gods Destroy").
	Bolian fingernails are darker in the crescent-shaped area in which human nails are brighter. Note that on the picture the blue make-up on the little finger is already partially gone (VOY: "Learning Curve").

Aliens with Other than Five Fingers

Certainly one way to create a distinct alien look is to give a species more than five fingers or less.

Six fingers Six fingers per hand seem to be a very rare trait.

Kolos' race has six fingers (DS9: "Q-less").

Four fingers We know of one special case where the thumb and the forefinger are coalesced.

	The Yridian thumb is grown together with the forefinger. Hence, they are four-fingered (TNG: "Birthright I", DS9: "Business as Usual"). There are also Yridians with five fingers though.
	Races with Changing Faces - Yridians

Three fingers There is a variety of three-fingered hands or claws.

	The Traveler from Tau Alpha C possesses just three fingers (TNG: "Where No One Has Gone Before", "Remember Me").
	Caldonians have three fingers, which are usually adorned by rings (TNG: "The Price").
	Antedeans have three fingers too, with big white fingernails or claws (TNG: "Manhunt").
	The inhabitants of Tarchannen III have three fingers (and three toes). It is one of the first steps in the transformation process into such a creature that the three central fingers of an affected humanoid grow together (TNG: "Identity Crisis").
	The Solanogen-based lifeforms exhibit three fingers with long, insect-like claws (TNG: "Schisms").
	Reptohumanoids have three fingers with reptilian claws (VOY: "Parturition").
	Furthermore the dinosaur-like Voth have just three fingers (VOY: "Distant Origin").
	The M-113 creature (the "Salt Vampire") exhibits a multitude of suckers on its three fingers (TOS: "The Man Trap").
	The CGI Gorn in ENT: "In a Mirror, Darkly, Part II" has three fingers. The Gorn captain in TOS: "Arena", however, had five.
	Races with Changing Faces - Gorn

Two fingers These races have a thumb, and the other fingers are coalesced to one.

	The Malcorians possess no more than a separate thumb, while the remaining fingers are all grown together (TNG: "First Contact").
	Likewise, the Parada have just two fingers (DS9: "Whispers").

Anomalies Two races that don't fit into the other categories.

	Vidiian hands are as diverse as the species from which the disease-ridden Vidiians steal them. The hands look just as cluttered as the rest of their bodies.
	Tellarite hands are inconsistent. They can be seen with three-fingered claws in TOS and with human-like hands on their later appearances.
	Races with Changing Faces - Tellarites