Yes it's from Bethesda.  They hinted at a surprise earlier coming with the Creation Kit.  I believe it's around 3 GB in size so it should contain higher resolution assets for much (all?) of the game's textures.  Thus, on PC, it should look even better that before and feature assets beyond those on console versions.

I'll wait for some comparison screemshots though to see if the difference is worth any performance hit.

Wow. The high resolution texture pack really makes Skyrim a lot prettier.

Stuff that is just bland and uninteresting in the regular textured game looks brilliant and interesting with the high resolution texture pack.

It might be me overreacting to this, but I seriously love it. The difference from Oblivion to regular textures Skyrim seems about as large as the difference from regular textures Skyrim to High Resolution Textures Skyrim to me.

Not a big difference between old and new textures but it's nice that they're offering this anyway.

It's not a huge boost to be sure.  I notice it most either outside in bright daylight or inside in terms of sharper objects, but it's not a massive change.  Still nice though as a freebie.  Does kind of make me wonder why the textures weren't on the disk though for PC in the first place but I won't sweat it.