This plugin makes possible to craft custom heads with block textures, also named as "Octablocks". They are very useful for building and nature decoration. Most solid blocks can be turned to octablocks with same recipe (differs only with main block material), except some transparent blocks (glass) and include cake.
Warning — it uses invisible armor stands for correct block drop (custom name and lore), so killing armor stands will cause non-valid drop (all dropped octablocks will be named as "Player Head" without lore).
Another Warning — heads render all their sides without culling, so if you use too much of them it will cause client fps-drops.
Original idea of octablocks was published on official Minecraft feedback site. You can support it if you want them actually in vanilla game.