Well, in my opinion for the setting, All I'd really ask is that it not be a traditional Holy Grail War. That is, I'd like there to be some kind of common goal or enemy among the players instead of it being the players fighting for the grail. But I really don't care for PvP so yeah. And I think the title will go right along with whatever the setting is.

As far as character skeletons I'd say that the Servant sheet format could look something like this. 
[hider=Servant CS Prototype]
Character type: (Obviously Servant.)

Statistics
Class: (Lancer, Saber, Archer, etc.)
Spirit: (Whatever the heroic spirit's name.)
Master: (Master's name.)
Alignment: (Good, Evil, Righteous Good, whatever best describes the servant I guess.)
Strength: (These statistics would be filled by letters from F to A+, just to be used as a general indication.)
Mana: (See above.)
Endurance: (See above.)
Luck: (See above.)
Agility: (See above.)
Class skills:
 (Anything related to the Servant's class, I'm pretty sure certain classes have default abilities.)
Personal skills:
 (Any specific skills, traits or abilities.)
Noble Phantasms:
(List of Noble Phantasm(s) and what they do.)

Information
Appearance: (Picture or description.)
Personality: (Just generally how they act, don't have to be terribly specific I wouldn't think.)
Gender: (Duh.)
Birthday: (If they don't have a definite birthday you could just put unknown.)
Height: (Take your best guess?)
Weight: (Same thing I suppose.)
Blood type: (Probably Unknown as well.)
Place of Birth: (France, Greece, Ireland, etc.)
Likes: (Yup.)
Dislikes: (Obvious.)
Talents: (Talents such as Martial Prowess, Hiding, Horseback riding, etc.) [/hider]