is there a version where the tiles are creating seemless surface? (the tile borders are not visible at least not obvious)
Viewing post in Tile Rivers, Coasts, & Seas Terrain comments
Unfortunately, no.
I'll explain: doing a seamless terrain style would require a re-design of the basic assumptions of the set, or a ton of additional asset requirements (by a factor of more than 2, at the very minimum). To avoid that, I could draw all basic land as the same biome - but that's contradictory to having all the deserts, marshes, snow, etc, or I would have to create transition edge sprites for *all* basic terrain types (and there are an awful lot), ...or I'd have to redraw all terrain types as seamless textures (plus variations?) while unloading transition effects onto the graphics coding side as some kind of shader (then I'd still have to draw edge transition masks, probably).
Basically, in starting these sets, I made the decision that they had to be tiles that could be slotted together easily as a what-you-see-is-what-you-get sort of system (and the coasts/rivers complicate this greatly, exposing the dangerous limits of trying to add very specific effects to a very generally-oriented tile system). To do something seamless would require starting from the beginning while prioritizing a different design goal.
Sorry!