So in a fit of creative boredom, I fiddled around a bit with the OpenTTD code to try and achieve something interesting. Click on the pictures for non-scaled-down versions.
This begs the question (well, I'm not sure it does, but it is an interesting question nonetheless) - what is the minimum size for a map in order to have a playable game - i.e. connecting a source and a consumer with a form of transport to earn revenue?
Another question - what is the minimum size for a map to have a playable game where the user can earn revenue AND be profitable on "standard" latest stable release settings?