There are many ways this could be approached, but you’ll want to identify the actor as interactive in some way. You can make them a specific class, like an ‘Interactible’ class for example. You can put a sphere overlap collider on your player character and when it overlaps, cast the object to ‘Interactible’ and if it’s successful, have the Interactible object add to itself a billboard image component. You could do it with a widget component as well, but you can achieve it in a more simple manner.
Just don’t put the collider on the interactive object because it’s better to have one object checking for overlaps that dozens or hundreds.