Versions:
0.1-
Texture Pack Started
Enderman is a Slenderman

0.2-
New Lava texture
New Emerald Block texture
New Iron block texture
New Gold block texture
New Diamond block texture

0.3-
Ore textures changed

0.4-
Improved sword textures

0.4.5-
Christmas Edition
Grass is white as if it snowed same with leaves,vines, and grass

0.5-
Pickaxes have a new texture

0.6-
New Creeper Texture

0.7-
Cobblestone Improved

0.8-
Improved grass texture
Improved Dirt Texture

0.9-
CTM glass support

1.0-
The rest of the blocks in the page were changed

1.1-
Added a few secret textures

1.2-
Ores have been changed

1.3-
Changed a whole lot of items, blocks and more!

1.4-
Few Ore changes and stone changes

1.5-
New Cobblestone texture
New Stone texture
New Stonebrick textures
New Lapis Block texture
New Nether Quartz textures

1.6-
Paintings are now themed to the pack.

1.7-
A new x32 version (Work in Progress) (Possibly a x64 version later)(Later removed)
A few blocks were changed
Sandstone, Sandstone Smooth, Sandstone Chiseled, Cobweb, Beacon, Wood Planks, and more
SlenderCraft on the main menu improved
Clouds have been added
Natural Texture Enchancments
CTM temporarily unsupported

1.7.1-
1.6 Ready
New Water and Lava animation
New Fonts
Removed x32 Version
Lang files edits
Fixed Slenderman's Head Glowing without Optifine

1.8-
New leaves textures
Biome specific coloring
New sounds Slendermen has noisy static noises and walking sounds
Splashes

1.9-
CTM Support
New Splashes
Slenderman's tie is now black
Fixed Torch Texture
Paper is now called Page
Paper Texture Changed
Custom Skies
New CreepyDark Edition of the Pack

1.10-
Removed sun texture from CreepyDark edition
Icon changes
New CTM textures
New Wood Plank textures
New Nether Textures
Enchanced Command Block texture animation
Brightened Lava
Brightened Fire
New Glowstone Texture
New Mushroom Textures
New Zombie Texture
Improved Camera effect
Improved Water texture
Few More Splashes
Language edits
New Eye of Ender texture and is named 'Slender's Eye'
New Ender Pearl texture and is named 'Slender's Pearl'
New Ender Chest texture and is named 'Slender Chest'
The End is now called Slender's Realm
New GUI
New Farmland textures
New EnderDragon Texture and named 'Slender Dragon'
New Ender Crystal Texture
New End Textures and end stone named 'Slender Stone'
Improved Mossy Stone texture
New Background texture
New Panorama in main screen

2.0- *Major Update*
Few New entity Textures
 .New Villager Textures and witch texture
 .New Creeper Texture
 .Ender Chest textured for real this time
 .Fixed Zombie villagers heads being invisible
 .New Steve (Char) Texture
Several New Item Textures
 .Almost every single item texture was changed
Few New Block Textures
 .New Hardened Clay textures
 .1.7+ Compatible
 .Improved Ladder texture
 .Made Non-CTM dirt look more like the CTM dirt
 .Changed Mycelium Texture
 .New water Texture
 .New CTM Snow Texture
 .Pumpkin a Camera and is named Camera
 .Jack o' Lantern a TV and is named Staticed TV
New Armor Texture
 .Chainmail Armor Changed
 .Diamond Armor Changed
 .Gold Armor Changed
 .Iron Armor Changed
 .Leather Armor Changed
Other Stuff
 .Enchanced Biome coloring and made it work better for future Minecraft releases
 .Nether Portal texture is more reddish
 .More Custom Colors with Optifine or MCPatcher
 .Custom sky coloring, fog coloring, and water coloring
 .Updated main screen logo, mojang logo, and resource pack logo
 .Updated torch lighting to be more reddish and realistic than yellow and it makes it more creepy on moody
 .Changed the enchanted glow texture a bit
 .Made an HD font for non MCPatcher and Optifine fonts
 .New Splash
 .Enchanced Rain sounds (They don't have a buzzing noise in the sound anymore)
 .New Stars in Custom Skies (You can see faint nebulas in the night sky[even some with faces if you look hard :D])
 .Changed the vignette to make darkness feel more creepyish(You need to have fancy graphics on in order for it work)

-2.1
Blocks Changed
 .1.7 Textures Completed
 .Redone torch and renamed it Lantern
Coloring
 .Enchanced fog for the new skybox texture
 .Redone Lightmaps to give the pack more of a modern horror feeling
  .Caves are much more darker
  .Lighting is now whiteish
Particles
 .Removed Smoke Particles
 .Done Fire particles to match with the torch
Sounds
 .Fixed custom sounds not playing in 1.7 Pre-release and above
Otherstuff
.Made a custom skybox for day to simulate a more realistic sky coloring(MCPatcher or Optifine required)[It makes the sky above look more darker and the horizon lighter]{Will be improved a lot more to look even more realistic}
 .Removed Vignette