You should set a variable storing correct path (url) on enter and exit fullscreen, and than use it in your action. Even if you will load new pano, the variable still be set correctly.
You can also test fullscreen mode in your action to showing pictures, and create url dynamically. Something like this:
<action name="showPic",">
if (fullscreen, set(path, 'images/highres/'), set(path, 'images/lowres'));
textadd(path, %1);
</action>
if you call this action like this: showPic(house.jpg), you will get path "images/highres/home.jpg" (if fullscreen is on) and "images/lowes/home.jpg" (if fullscreen is off)
This is an idea of corse, not complete code.