Sure,
Well, how about we all throw some hints and ideas in for your design
If I'm wrong about any of these, i'm hoping someone will correct me

- that way we will both learn!!
Roche's Hints for Studio Design - probably incorrect, but waiting for someone else to have better one's
1) Try to avoid parallel walls - they are bad, and can cause reflections.
2) if you angle each wall about 12 degree's away from center (take a look at many of Johns designs) then you can avoid parallel wall problem.
3) Remember that the floor and the ceiling are "walls" as well. *many* studio's have a ceiling with at an angle.
4) Try to balance out the decay/echo time accross all frequencies. Decay time is the time taken for a sound to die away (i think it's 60db's.. unsure.. RT60 and all that).
Some rooms sound really bassy and 'muddy' - this is normally because the low frequencies are taking a longer time to die away than the higher frequencies.
5) Balancing out decay time's can be done with absorbers. I'm sure I read somewhere at the SAE Website that a room should contain as much low end bass absorbers as possible. Maybe I was dreaming again...
6)You want to make the room, so that once the sound has passed your ears (as engineer) - that the sound won't come back

This is usually done through absorbtion and diffraction on the back wall.
Let's see if anyone else can add some hints for you
Cheers
R