This might be a little bit of a stretch, but I was noticing how strangely sparse the pumpkin fields are. Seems like there is only tall grass spawning when other biomes such as the maple forest.

Also, if you are adjusting the decorator, perhaps regular mushrooms could spawn in the field? It could fill it out a bit. Feel free to close if this isn't in line with the vision for the biome.

After a quick chat with the Terra Incognita devs, it seems like their plants should be spawning in the pumpkin fields as well, and it seems like Autumnity might be suppressing that decoration as well.