Q1. How long should the challenge run for?

1 to 2 months at the discretion of the challenge setter who should also take extenuating circumstances into account. Things like time of year, holidays and such.

Q2. Should contestants be allowed more than one entry?

One challenge, one artist, one entry.

Q3. Should there be restrictions on size. IE: 800 x 600 etc. ?

I concur with Weezer…800x600 on the board with option to view full size if this can be made possible.

Q4. What would be the best time for the entry deadline? (12 noon, 12 midnight etc)

This is a little thorny because not all members come from the same global location. New York is typically 5 hours behind London whereas Bangkok is 6 hours before London and Phoenix Arizona is 3 hours behind New York and so forth. If this can be decided then I would have to say Midnight.

Q5. What would be the best time to end voting? (12 noon, 12 midnight etc)

If we can decide on what to do about question 4 then I would agree midnight.

Q6. How long should voting be allowed? (2 days, 3 days,...)

3 days.