“Header Image Replacement under Featured Image ” replaces the header image.
Your header is made with a slideshow inserted in the header HTML which has nothing to do with the header image.
If you only have one page where you want to replace the slideshow by a header image, you could do the following.
Insert both the slideshow AND the header image in the Header HTML, each in a show_if shortcode that will display them when wanted.
Given the page you want the header image on has the id 25, it would look like
[show_if not_post_id=25]Slideshow shortcode[/show_if][show_if post_id=25]The header image for page 25[/show_if]
Check the add-on page for the shortcode syntax details.
If several pages will have the same header image instead of the slideshow, you can list their id separated by comas in the shortcode.
If several pages will have different header image, then we can look at a simpler solution for that