I'm actually really interested in this project, and I went back last night and examined all the differences in detail to figure out what's putting me off about the new tiles.
The biggest issues I had were with the sand and desert badlands tiles. Also, in areas where there's a dominant biome that has one and two tile pockets of another biome interspersed it really looks off.
However, I also realized on inspection that these were the same issues I have with the ASCII maps, except for sand. I think the sand looks great in ASCII because the ~ characters give the biome boundaries kind of a 'ragged' look. I also just hate the mayday sand tile, it's just awful and doesn't look anything like sand.
Sizik, since this is not meant to be used in game, how about multiple versions of biome tiles that are used dependent on the bordering tiles?
For instance a sand tile surround by other sand would be the normal rectangle, but if the sand tile is bordered by another biome you could have a 'ragged edge' version. Of course that would require map analysis prior to rendering, I don't really know if you're willing to go that path or are strictly in this to develop new artwork.
I'll keep thinking on this but I like the way you're going. I would love to have a more realistic map just to look at, I'm a huge map nerd and am slowly developing in my mind a comprehensive 'DF World Viewer' type concept. I've already spent countless hours just genning and looking at worlds, using the detail maps and that terrain viewer as well as the normal maps like these. If we ever get Legends export I would probably never play the actual game again, just continually gen worlds and read histories.