Strait Mod 1.12.1, 1.11.2 just makes it possible to place item frames on the bottom or top of blocks.
There are some things to note. Compasses will point the right direction in frames above blocks (i.e. on the ground), but not in frames below blocks (i.e. on the ceiling). That cannot be fixed with making Strait a core mod. Maps placed in frames will be represented by a pointer on the map that points south. If you want to make a map room that has maps wrap from floor to wall or ceiling to wall, a small portion of the map won’t render because item frames are raised a bit off the block.
How to install:
Strait Mod 1.12.1, 1.11.2 Download Links:
For Minecraft 1.9.4
For Minecraft 1.10.2
For Minecraft 1.11.2
For Minecraft 1.12.1, 1.12