Your App Logo (the logo image you will use for your app’s homepage, splashscreen & navigation bar) must be in a SVG format.
Why? SVG files don't drop in quality when their dimensions are significantly altered, which gives them the best resolution across various mobile devices.
If you are unable to find your App Icon in the correct format, please feel free to use one of many online file converters to get this image to us in an SVG format.
For your convenience, we've linked one that we feel works quite well here.
Important Note: The original SVG image that you would have received from the person who created your logo is the best quality image you can use for an App Icon. Converting the file will work fine for our purposes but the quality of your image will be comparatively degraded.