Null walls and biome-type options would do wonders for the boxes. Of course sizes too, but that seems more complicated.
actually new biome designs in current boxes for existing animals will require similar amount of work unless they use same designs used by other animals
for example iguanas or snails probably wont be in the same design as puff adders despite also being grassland
i'm guessing they will require a new layout even if using similar textures
either way i think this is a very needed feature.. both for existing size and hopefully new sizes
