Map has maximum size avaliable in the editor.
There is main island, few smaller islands and some other underwater objects. Some places can be reached only when your flying or diving skills are high enough. There's also a plot, and you can actually "win" the game.
Some hints:
Spoiler To build up flying skill you need to fly or climb above certain altitude. You need to use trees or other high objects first, then you can build kites - each kite increase your flying skill with every passing day. Finally, you can use wings and/or glider.
Spoiler To increase swimming skill, you have to dive to your current limit. That means, the higher the skill, the deeper you have to dive.
Spoiler Last new skill - pyrotechnics - can be increased initially by building fire arrows or making a fire.
Spoiler A new tool - prospective hammer - when used on rocks reveals minerals deposit. You won't get any saltpeter or sulfur from a rock before you prospect it.
Spoiler Beehive is very important objects - you can gather wax and honey, two new materials crucial for making new items. Try to combine them with cauldron (a new item, yes) and fire, and maybe some other materials, and see what you get. I made some research prior to making this mod, and I think combinations are not too diffcult to find.
Bees are difficult to kill, and the best way to get rid of using smoke bombs.
Spoiler You can obtain fiber from a bark. Fiber is then used for making a paper.
I think that's enough help for now.
PS.
Spoiler Dead bees are also usefull... Store lots of them, maybe you'll find someone who likes them.