Hello @chevaldessteppes,
Actually, the banner image that appears in the header i.e. on page title bar is controlled from the theme and we are not quite sure which theme you are using.
Also if you have used the travel log theme then there is no such option to set different banner image for the different trip page but however we can provide you custom code, using which you can set the different banner image for the different page where the banner image comes from the featured image section of that page.
For this you have to activate the child theme. You can activate the child theme manually or simply activate using the plugin given below:
https://wordpress.org/plugins/wp-child-theme-generator/
After activating the child theme in your child theme functions.php file add below-given code.
https://gist.github.com/anonymous/d57b71b78bade2892db1fc1bad40a588
Hope this helps.
Best Regards!!
Have a good day 🙂 .