Visual assets templates for Windows Phone Store apps now live!
I previously published these (temporarily) right here on the blog in case that unblocked anyone, but now they're live. If you go to the Windows Developer Center (dev.windows.com) and click Design > Design downloads then that takes you to this url: https://dev.windows.com/design/assets. There are lots of great resources there for Windows Store apps and Windows Phone Store apps. On that page, in the Windows Phone Store apps section, is a new link under the heading "Visual assets templates". Using that link you can download the zip file here: https://dev.windows.com/design/assets.
Inside the zip are files (in .psd and .png format) to get you started designing your visual assets for your Windows Phone Store app, including app bar buttons, app and store icons, file type and protocol association icons, hub background, splash screen, and start screen tile icons. There's also a .pdf file that shows an overview of all the assets, backgrounds, colors, paddings, and so on.