The full complete changelog for Minecraft 1.12 changes can be found at 1.12 – Official Minecraft Wiki
This is a short list of the most useful additions for MCME.
Achievements have been removed and replaced with Advancements.
Mojang added a costumizable system to add your own advancements through json files. An immediate idea that came to my mind was adding Advancements for each major area, as you can make the server check if a player is in a certain location and add an Advancement if he is in a certain radius. A full list of triggers is available at Advancements – Official Minecraft Wiki
Saving creative toolbars.
Toolbars can now be saved in creative mode with C+1-9 and loaded with X+1-9.
Minecraft Functions.
There's a new system that can run arbitrary minecraft commands and these functions are saved on the server as a .mcfunction file. Functions are basically a list of commands (though expect turbopascal style, there is no control flow)
New sounds.
New note blocks sounds have been added for bone block, gold, clay, packed ice and wool.
Blocks.
- Sixteen new concrete blocks (which is a solid non-physic form of concrete powder blocks)
- Sixteen concrete powder blocks (which act like sand -> gravity)
- Sixteen glazed terracote blocks (has 4 block rotations depending on player position similar to pistons)
Banners.
Use an updated color palette (colors are still the same but hue has been increased on some colors)
Fances, Cobblestone Walls, Glass Panes and Iron Bars now connect to stairs.
This could be a breaking change in some situations I suppose on the build server.
Paintings will now try to place the largest painting possible.
Stairs' rear face and underside are now considered solid and allows for torches, fences, ironbars, glass planes, walls and snow layers to be placed upon/connected.
This is a short list of the most useful additions for MCME.
Achievements have been removed and replaced with Advancements.
Mojang added a costumizable system to add your own advancements through json files. An immediate idea that came to my mind was adding Advancements for each major area, as you can make the server check if a player is in a certain location and add an Advancement if he is in a certain radius. A full list of triggers is available at Advancements – Official Minecraft Wiki
Saving creative toolbars.
Toolbars can now be saved in creative mode with C+1-9 and loaded with X+1-9.
Minecraft Functions.
There's a new system that can run arbitrary minecraft commands and these functions are saved on the server as a .mcfunction file. Functions are basically a list of commands (though expect turbopascal style, there is no control flow)
New sounds.
New note blocks sounds have been added for bone block, gold, clay, packed ice and wool.
Blocks.
- Sixteen new concrete blocks (which is a solid non-physic form of concrete powder blocks)
- Sixteen concrete powder blocks (which act like sand -> gravity)
- Sixteen glazed terracote blocks (has 4 block rotations depending on player position similar to pistons)
Banners.
Use an updated color palette (colors are still the same but hue has been increased on some colors)
Fances, Cobblestone Walls, Glass Panes and Iron Bars now connect to stairs.
This could be a breaking change in some situations I suppose on the build server.
Paintings will now try to place the largest painting possible.
Stairs' rear face and underside are now considered solid and allows for torches, fences, ironbars, glass planes, walls and snow layers to be placed upon/connected.