I don't see how one can cycle through the objects in the PDF document in PDF::API2. From what I see, it gives you the ability to add objects but not browse through current objects.

What would be useful in your case would be the ability to cylce through all objects in the document and if the "Type" of the object is "XObject" and "Subtype" is "Image", then you know you have come across an image.

-imran