Dalek variant

While the basic appearance of Daleks remained the same throughout their history, there were several changes and alterations to Davros' original design of the Mark Three travel machine. Variants of the "basic" Dalek design were produced both by Davros and the Dalek Emperor/Dalek Supreme (these last two representing the major power holders in the Dalek hierarchy). Both factions of Dalek used a Dalek drone for basic combat.

Davros' variants
Early in his design work Davros created Spider Daleks, which walked on a set of spider-like legs, rather than gliding across the ground. These were succeeded by Daleks known as "Strider Daleks". (PROSE: War of the Daleks)

Following his awakening from cryogenics and an encounter with the Dalek Supreme, Davros set up a base of operations on Necros and began creating Daleks of human origin. As the name suggested, these Dalek variants were created using humans, rather than Kaled mutants. This process also employed a Glass Dalek. (TV: Revelation of the Daleks)

Dalek Emperor / Dalek Supreme variants
The Dalek Emperor and Dalek Supremes were marked by having several designs that differed significantly from other Daleks. They also created altered designs under their own command.

Dalek Puppet Emperors also existed. (PROSE: Meet the Doctor)

At the command of the Dalek Emperor, the Cult of Skaro were created. (TV: Doomsday)

Shared design variants
Both Davros and the Dalek Emperor were known to use Special Weapons Dalek variants in combat situations: Davros used one during the Shoreditch Incident, whilst the Dalek Emperor utilised several in various campaigns. (TV: Remembrance of the Daleks, COMIC: Fire and Brimstone, PROSE: War of the Daleks, AUDIO: The Genocide Machine)

Last Great Time War
The Eternity Circle created the Predator Dalek, intended for the War Doctor to become its Dalek Mutant. (PROSE: Engines of War)

A unique unit during the conflict was the Dalek Time Strategist, the successor to the Dalek Time Controller, its casing a purple coloured variation of the red Dalek Supreme model that first appeared in the Second Dalek War. (AUDIO: The Shadow Vortex)

Post-Last Great Time War
Following the Last Great Time War several new Dalek variants were created, both embryos, not technically a variant, but rather an attempt to recreate the original Dalek mutation. (TV: Daleks in Manhattan)

Following Dalek Caan's intervention, a new Supreme Dalek was created, along with Vault Dalek to guard and maintain the vault of the Crucible. (TV: The Stolen Earth)

After the fall of the New Dalek Empire, a trio of Dalek drones, (PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe) found themselves stranded in 1941. They concocted a plan to have the Eleventh Doctor identify them as Daleks to the Progenitor, an ancient Dalek instrument containing "pure Dalek DNA". The Progenitor created five new specimens, with five larger and colour-coded cases, new variants of the Supreme, Scientist, Strategist and Drone Dalek along with the unique Eternal Dalek. Naming themselves the New Dalek Paradigm, these five proceeded to destroy their "inferior" forebears, and fled to parts unknown through a time corridor to start anew a restored Dalek legacy. (TV: Victory of the Daleks)

While the New Paradigm initially mass-produced its new design of casing, (GAME: City of the Daleks, COMIC: The Only Good Dalek) the many defeats that the Eleventh Doctor would go on to inflict upon this design caused other species to lose their fear of the Daleks. Reorganising their command structure, the Paradigm reestablished the Parliament of the Daleks under the leadership of the Prime Minister of the Daleks who promoted the Paradigm's first style of casing to a seldom seen "officer-class" and returned the active infantry to the designs used in the Last Great Time War. The five founders, retaining their original casing design, were reduced to a token presence in the Parliament with several Red Drones overseeing their bronze subordinates. (TV: Asylum of the Daleks, PROSE: Dalek: The Astounding Untold History of the Greatest Enemies of the Universe)

In time, the Paradigm casings seemed to vanish from the post-War empire. Instead, bronze casings remained the standard design of drones, while Black Dalek and the red Supreme casings re-emerged as officer classes. Older casings designs like the Dalek War Machine and Imperial Special Weapons Dalek also returned. (TV: The Magician's Apprentice, The Witch's Familiar) Death Squad Daleks and Dalek Executioners used bronze casings. (TV: Revolution of the Daleks, Eve of the Daleks)