As for #1, in the source code itself you can set all 6 sides of a block's textures, hence the issue I'm hitting where I'll have to make a tileset that's just the base tileset amped up, and a "mod for a mod" version that is recompiled source with my modified changes.
If you're refering to the sprites array then the numbers don't all represent individual faces, the order is:
- Inactive bottom
- Inactive top
- Inactive sides/back
- Inactive front
- Active bottom
- Active top
- Active sides/back
- Active front
The value for these can be changed without overwriting IC's class files, howeverto seperate the back and side textures would probably need you mod IC's file directly.