I think for the polycount, we should choose. I am on a 300MHz proccessor, so I can't handle to many polys. But in the end, I do not want to hinder you with it.
I think we should leave out texturing. First of, I am new to UV mapping, and I do not know how to map them yet, and second, we would have more time on the model.
For the idea, what about some space vehicle, space ship, futuristic battle machines such as anti-gravity tanks and such.
And for the tim elimit, is one week enough for you? I have holidays off school in the next week, so I have time if you want it longer.
EDIT: For the textures, we could have it as obtional, but thats up to you.