FileTypeAssociation Logo sizes for Windows Phone 8.1 modern apps
The MSDN documentation on “How to handle file activation”, for Windows and Windows Phone 8.1 applications says that Logo images should be of sizes 16, 32, 48, and 256 pixels square. The MSDN documentation on “Auto-launching apps using file and URI associations for Windows Phone 8” says that Logo images should be of sizes 33, 69, and 176 pixels square.
However, none of these sized images work correctly when used in a Windows Phone 8.1 (XAML) application. Instead you need to use image sizes: 36, 129, and 336 pixels square. Since this is phone specific you should add these to the Windows Phone specific assets of your Universal project. The filename must be in the form: <name>.targetsize-<size>.png, for example:
You need to reference this set of files in your Windows Phone 8.1 projects’ “Package.appxmanifest” file using just the first and last parts of the file name, without the “targetsize-*”, for example: “Logo.png”.
FYI: “Display name” and “Content type” fields are not required but nice to have.
Now, after you deploy the app to your phone any files with registered extension (“.alsdkcs” in this case) should show on of your Logo images in applications which support display of the file type logo like the Office Hub.
NOTE: if multiple applications are registered for the same file extension then you will see a search icon: 
instead of either applications’ logo.