The in-built image gallery function in WordPress is very useful, in that you can create great looking image gallleries with a few clicks. Here’s an example below of a WordPress gallery.
An example WordPress Gallery
However, by default WordPress will include every image you include in a post or page to your image gallery. This can be frustrating when you want to show another image but don’t want to include it in your gallery.
How to exclude an image from an image gallery
The trick here is to upload your image into your Media Library first. Once you have uploaded your image to your Media Library just click save, then go back to your post (or page), click the image upload icon and then select your image from the Media Library link. And bingo, you will now be able to add your image without it appearing in your Gallery.
Example picture in a post that is excluded from the image gallery