For a larger preview of the tiles, click here.
For a .pdf with correctly scaled tiles and full (work in progress) rules, click here.
I've been toying with this idea for a while, and finally got around to making the tiles today. The tiles form the coast of Carcassonne, which - like the River - is built at the start of the game. There's also room for up to two rivers that flow into the ocean, although these shouldn't be placed side by side. This gives the region one clearly defined border, which can be helpful when playing on smaller tables.
There are also some special rules. Features bordering the coast or the river have a neat function - when they're completed, the scoring player may place a (normal) meeple on a road or city occupied by another player (provided that the current player does not already have a follower on this feature.) Coastal farms are scored immediately, but are worth less points. And the tiles with the pirate skull symbol are used to kick players out of coastal regions, making them a high-risk area.
There are a few things I'm not sure about, and probably need play-testing. Firstly, I'm not sure how many coastal tiles should be used per game. Secondly, I'm not sure if I've got too many or too few coastal tiles that divide the field. Thirdly, I'm worried that the pirate skull tiles will feel completely unfair for people on the coastal region.
Thoughts, comments, suggestions?