On Friday, Bethesda's Pete Hines tweeted that the Creation Kit is on track for release tomorrow, adding "we also have a special surprise with it." Horse armor jokes aside, it appears that surprise will be an official Skyrim HD textures pack.
Player Attack directs us to the official Skyrim forums, where a poster that goes by the name of Bonehedge claims to have discovered evidence of the HD texture pack in the Steam Content Description Records. Here's what he found:

We'll find out for sure when we unwrap tomorrow's Skyrim surprise ourselves.