The 'Donate Image' button shows on Special:Uploads on Windows Phone 8, but tapping on the button has no effect.
Tested so far in the SDK emulator, not yet on an actual phone -- should double check on real device.
It looks like IE10 on Windows Phone 8 doesn't support file uploads per http://blogs.windows.com/windows_phone/b/wpdev/archive/2012/11/08/internet-explorer-10-brings-html5-to-windows-phone-8-in-a-big-way.aspx
So we should see if there's a clean way to detect it's not supported. <input type="file"> looks like the traditional file input control on Special:Upload but also does nothing when tapped.