Question: I have a button with image.How can I localize it, in order it to have another image on different language ?

Answer: 
Are you loading the image from a Storyboard or programmatically?

If programmatically, then you can localise the string of the file name and have different images for each localisation.
You can add localized names for your images to Localizable.strings file and use "NSLocalizedString(key: String, comment: String)" method to access it. Works great for me.