Probably these have been suggested a million times but I'm not gonna go through all the 666 pages, sorry-not-sorry. x)
Here is a bunch of additions from a builders perspective:
-Stairs and slabs for wool, terracotta and concrete
-Painted wood planks and stairs/slabs/fence variants, no need for every wood type, just one type of painted wood planks
-Variants for remaining stones; andesite, diorite and granite. Bricks, cobblestone, wall, slabs, stairs etc.
-Furniture: tables and chairs at least, all wood types and also one gray stone variant. Maybe an armchair->sofa also from wood and wool.
-Rope to line between blocks for fence and bridge purposes
-THE STICKY PISTON SHOULD BE STICKY SO WHY DOES A CARPET PLACED ON TOP OF IT POPS OUT WHEN THE STICKY PISTON IS PULLED BACK DOWN!?!? Damned.
-Different colour bricks, with a natural colour palette same as terracotta
-New mobs for different biomes and purposes; foxes dig under blocks and kill chickens, squirrels climb trees and drop seeds, deers for leather and antlers (bone), buffalos for leather and meat, goats for milk and wool, snakes for danger, some big cat like cougar or lynx for danger, mice/rats to ruin your unprotected harvest, also tameable trashpanda would be awesome, it could steal small amount of goodies from villagers and from player when not tamed
-Craftable saddles now seriously, make it hard if you have to but make it possible
-Big flower pot, outside looks like pot, inside tilled soil. Works like dirt/grass block. For inside gardening and decorating with double tall plants without the space requirement for trapdoors on sides.
-Possibility to place flower pots, brewing stand, torches and mob heads on half slabs