Several people asked me if there's something interesting about the design of other characters and yes almost for every character I can tell something extra, so I decide to share
WHAT IS NOT SPOILER with everybody instead of keep it in PM.
All the design in the fate universe is done by Naoko Takeuchi, while Nasu and Urobuchi write the stories.
Some characters existed even before the story was written for them and some are created to fill a spot in something they wrote.
I talk you guys about rider already so now we can talk about saber.
As you guys know the fate zero anime is a recreation of the novel under the same name but you guys maybe don't know that when all the idea around the fate universe was created when the whole thing was just a project, a few characters were a little different.
For example King arthur was a male not female.
And even later when they decide that she should be a girl her appearance was not as we see now.
In the next image justlike with Alexander, takeuchi show us a little pic again of his first idea of saber. I think the first design was a little too close to another character from another type moon work so I think that's why he went on another direction. Although a saber with shorter hair would be badass.
Images taken from Fate/Zero character sketches book and Fate character material vol 3.
Edit.
Sorry I forgot the image of Caster you guys asked, here it is.