This can be done using a button field set to display an icon and a simple script.
However, only users of Reader XI or higher will be able to import a file into this button, and only those that have the very latest version of Reader DC will be able to select anything but PDF files as the image file.
The code to use as the button's MouseUp event is simply this:
event.target.buttonImportIcon();
However, I would recommend that you create this field in Acrobat, not in InDesign. The two applications don't "play well" when it comes to form fields, so if a field needs to be edited it should only be done in one application or the other, from my experience.