The technique used to display hovering text in game no longer functions in the latest snapshots due to improvements to the render engine.

However, summoning a stationary WitherSkull mostly still has the same effect like so:

/summon WitherSkull ~ ~3 ~

{direction:[0.0,0.0,0.0],CustomName:"Something something name",CustomNameVisible:1}

But when doing this, the texture of a wither skull will flash appear for a split second every 10 seconds or so.

Ideally the texture should stay transparent without any flashing when stationary, so that map makers can continue to use this technique to create immersive experiences.