Is it possible to have a retina download icon for adhoc/ota distribution?

Question

Having just discovered how to have our app icon show up during an OTA install I have learned that it is too fuzzy and we need a higher resolution icon. Find attached a version of the .plist file we are using. So far my research has turned up next to nothing and trying to add an "Icon57x57@2x.png" didn't work either. Is there a special key I need to add?

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>items</key>
    <array>
        <dict>
            <key>assets</key>
            <array>
                <dict>
                    <key>kind</key>
                    <string>software-package</string>
                    <key>url</key>
                    <string>http://downloadURI/app.ipa</string>
                </dict>
                <dict>
                    <key>kind</key>
                    <string>display-image</string>
                    <key>needs-shine</key>
                    <true/>
                    <key>url</key>
                    <string>http://downloadURI/Icon57x57.png</string>
                </dict>
            </array>
            <!-- metadata omitted for brevity sake -->
    </array>
</dict>
</plist>

Answer 1

Just put a PNG file with a size of 114 x 114 px at the referenced path. No need to use any special suffix. The image will be scaled if it doesn't match exactly, but this usually works well enough, so you won't notice a large difference to the app's actual icon.

If your app is universal, you may want to put an even larger image there to support the Retina iPad's 144px icons.