Though a few third-party hacks have allowed customers to make their home-tiles transparent in the past, Microsoft is rolling out the new feature for Windows Phone 8.1 customers. Microsoft has recently posted a short how-to guide for the process, “which allows people to set their Start screen to have a background image displayed behind the tiles.”
As Microsoft indicates, there is one catch of course, “There’s just one thing though… in order for users to see the image behind the tiles, the app’s tile needs to have a transparent background, so if yours doesn’t have this yet, here’s how to do it.”
If you are developing a new app, or if you have one already that you would like to enable the feature, here is a handy guide from Microsoft.
1) Use a transparent .png for your tile
2) For those of you already targeting Windows Phone 8.1, update the ‘Background color’ setting in your package.appxmanifest file, (on the “Visual Assets” tab), to ‘transparent.’ There are, by the way, many different free image editors out there to assist you in this, my own personal favorite is Microsoft Expression Design).
3) For a dynamically generated live tile, you’ll need to take an extra step: make certain that whatever mechanism you are using to generate your tile is building a transparent .png, (libraries like WriteableBitmapEx support this).
The feature probably won’t sell phones on its own, but if you do have a Windows Phone 8.1 device, then it is a nice option to make your start-screen a little more vibrant.
more info: microsoft