There have been some pretty good ideas posted so far. One that I liked was going with a very modern sci-fi setting. Something post- or near-Singularity, showing off the absurd variety and social upheaval that comes along with that, with flavors of Accelerando, Stand Alone Complex, Transmetropolitan, and Eclipse Phase. Gaming is weirdly slow to acknowledge that sci-fi written after Neuromancer exists.
I'd think 2d would work best. It'd fit well with the budget constraints, for one thing. I honestly don't think that full 3d adds that much, especially when current-gen AAA games with massive b