Not sure about a mod, but I will say that the larger the map, the more likely you are to get your start bias and lots of it. The larger the map, the more room there is per civ, so there are more places for each civ to get it's bias.
Also, smaller maps have less total room, meaning each feature is smaller (that is, jungles, deserts, mountain ranges, etc. are made up of fewer tiles). It's obvious if you think about it, but that means that on a huge map, Morocco might start in the middle of a desert that can support 4 or 5 cities totally within it's confines. Jungles, on huge maps, can often support a liberty wide start, with 5-6 tiles between each city, and each city with mostly jungle in them.
In my experience, standard size maps often give you your start bias, but the land changes so quickly that it doesn't dominate your starting area. Tiny maps give very little of any type of land in large enough quantities to take advantage of any type of land in one city. Huge maps give massive swaths of land that can really be abused by civs with a start bias that benefits them.