Chisel is a Minecraft mod by AUTOMATIC_MAIDEN which adds a huge amount of decorative blocks. Ported primarily due to the fact that MAIDEN's mods are under the GPLv2.
Added: Far more config-level configurability for the mod's available features and behaviour.
Changed: The config format. Cleaned it up a bit. Watch out!
Fixed: Marble stairs and limestone stairs now work!
Fixed: Partially attempted to fix the “left-click-with-chisel to make block disappear” bug.
1.5.2 (17 March 2014)
Added: Chiselable Stained Glass and Stained Glass Panes.
Changed: Textures are now compressed with pngout, cutting the mod's size from 4MB to 2.1MB - an almost 50% reduction!
Changed: The internal mod-specific names used in the GameRegistry. worlds saved with Chisel 1.5.1 will *not* be compatible, and worlds saved with Minecraft 1.6.4 and below probably will not convert perfectly as well, but this was done for the better - mod collisions could've and would've happened otherwise.
Fixed: NPE with certain blocks' rendering.
1.5.1 (16 March 2014)
Ported to Minecraft 1.7.2.
Added: Support for Acacia and Dark Oak planks.
Removed: Overriding vanilla blocks.
Minecraft 1.6.4
1.5.2 (18 April 2014)
Fixed: Marble duplication bug.
Fixed: Glowstone dust now drops and stacks properly from chiseled blocks.
1.5.1 (30 March 2014)
Fixed: The left-click-with-chisel-makes-blocks-disappear desync bug.
Fixed: Re-save your world with this version of the mod to get better 1.7.2 compatibility.
Fixed: Recompressed textures with pngout to reduce filesize (3.8MB → 2.1MB).