Minecraft Schematic?

I want to build a map in Minecraft. The problem is that Spirecraft is not intended for building maps, so there are some errors, e.g. Spirecraft sets pixels that are gray to cyan Terracotter. It also looks gray when you look at it, but the map is then light blue. Could anyone recommend another website / program with which one can build better cards?

I don't know if it's the name but lithium?