Pebble UI Template
Hands-down the best Photoshop UI template for Pebble.
Includes all of the available built-in UI elements, a high-quality render of the watch body (including the new Pebble Steel), grids (by Orviwan), and font information. And best of all, it's all done in vectors, which means you'll have no problems scaling this up to the size of a billboard.
Oh, and did I mention it's all available under the Creative Commons license? Booyah.