If i create a map with 1 biome color and use FromImage mode TC will generate all of the Default biomes but will not generate any custom biomes.

However if in Normal mode using only a custom biome TC will load only the specified custom biome.

I can change the HEX code for default biomes and they will still generate correctly.

I have the same problem. Biomes aren't generating based on image map, it is all default instead. I tried it with a copy of old 1.3.2 map, which was partially generated from image with 1.3.2 TC, i use the same configs which worked, but now, in 1.4.2, whenever i explore new areas, they are just default tc land.

So I understand that FromImage is broken under certain circumstances. Could you also show the map and the WorldConfig.ini?