Raymond Cusick worked on the original iconic Dalek design which unlike most other monsters including the Cybermen has been used to this very day.
The original design was more cylindrical as pictured below. Cusick then changed the design so that a seat could be fitted to allow the Dalek operator to sit down. Four Daleks were made originally in Shawcraft in Uxbridge costing £250 in 1963. Shawcraft Models made special props and effects for the first few years of Doctor Who.
Below is the original concept art for the 2005 bronze Daleks. Below is also a colour Dalek chart showing some of the variations originally thought about.
Below left is a drawing of how the inside of the Dalek could be displayed. The right image is an original drawing of how the Dalek space ships would look.
Below is the concept art for the additional weapons, the claw arm used in The Parting of the Ways and the instrument used in The Stolen Earth.
Below are the original drawings of how Davros and the Supreme Dalek would look in the 2008 story The Stolen Earth and Journeys End.
Below is the concept art for the Paradigm Daleks. The drawings show the major changes between the 2010 and 2005 versions.