I replaced all the images everywhere (by this I mean in drawable folders and all Windows Assets folders and iOS Resources folder), but it still shows me the default Xamarin
Answer is deprecated
If I understood you correctly, for iOS project: Properties -> iOS Application
For Android: Properties -> Android Manifest
Try to replace all the icon on iOS project > Properties > iOS Application > Iphone Icons/IPad Icons. I change all of them, the settings icon do change. Images that on Resouces can be created by just insert images on there.