So you change themes and the header image needs to be a different size. You upload the resized image, and then you realize something: In the new size, the layout of the graphic elements should be different.
You open your source file, make the changes, and then go to re-upload the corrected image. While you are in the media library, though, you see the old version and decide to delete it to avoid confusion at a later date. This done, you re-upload the file.
When you view your site, though, you see that the old image is still in place.What’s going on?
The cause is probably that the old image has been cached somewhere, and it is being served up instead of the new version.
The way to fix it is to change the name of the new version, upload that, and then set it as your header image (or as one of your header images, if you are using that feature).
The cache will recognize that the new name is different from what you have been using, and serve up the new image.