I was really impressed by the concept of pakMars, a couple of years ago.
If I had ever time, in an unforeseable future, I would like to mess a bit with it, trying new ideas and concepts.
If it had to be me doing something about it, I would probably go for a 128*128 tileset or even 192*192.
At the moment, i want to share this link, as it would be of great use for future discussion:
http://quest.arc.nasa.gov/mars/ask/humans-on-mars/
Very interesting link. As far as I remember, we already discussed some of the points (airplanes,water, etc...) at the old forum.
during or after terraforming mars?