Associated how? In the webmentions you send? Typically the receiving site will parse your page to find the h-card and pull out the u-photo for it, so depending on your theme or a custom marked up h-card, that will dictate the photo that shows up.
I have been noticing some issues recently with a lot of photos not showing up in webmentions I receive. Typically they’re for WordPress or micro.blog sites which may mean issues for Gravatar-based images.
If you want to fix them manually, a recent update allows this.Syndicated copies to: