Random map generation

I'm not sure I understand clearly. Is your intention to have certain areas of your map be generated with a high volume of of a particular tile, or to have individual tiles randomly dispersed across your map?

High volumes of a particular tile, not just single tiles at random spots

I see. In that case, I'd have to say my method would be choosing a single tile as the point of origin for the "hot spot", and working out to all of the adjacent tiles, reducing the likelihood that a given tile would be set to the chosen type. I'd imagine determining whether or not a tile passes the check to be transformed into the proper tile would be as simple as generating a random number (say, 5 for starters) and making the tile match the specific type to be set as long as the number is not equal to one. Then, with each move outward from the point of origin, reduce the ceiling for the random number by one. That way, as you move farther from the point of origin, the likelihood of a given tile following the pattern will diminish naturally.

Thanks for the info, I'll try that out :)

Hope it helps.

It's counter-intuitive, but I got rather good results just generating randomly and then converting the tiles based on whatever is around them iteratively. Ie, if a Water tile is surounded by mostly Land tiles, it becomes a Land tile - And vice-versa.