Here's the texture atlas of my custom 1.10 pack.

As you can see, TombManyGraves takes up a big amount of space in the middle area, wasting a lot of it with a single color texture.

Here's the new mod to dump textures if you want to try it out: https://github.com/mezz/TextureDump
Also: https://www.reddit.com/r/feedthebeast/comments/5b6bwg/exploring_the_texture_map/

Yeah, I completely forgot about that. I'll remove that in the next build.