As you know in UWP apps there are two themes Light and Dark, I have 2 custom Icons and I have target it as these qualifiers as follows: MyImage.Theme-Dark.png and MyImage.Theme-Light.png so it doesn't work for dark theme and it only works for light theme. How to target Images for two themes? what is the correct target of image for multi themes?
No, there isn't. These are just files or embedded resources that are part of a compiled assembly and a theme is just a resource dictionary of resources. You could indeed create a "Light" and "Dark" folder but all images in the Light folder will still be available for the dark theme and vice versa.