Thanks for trying out Tab2QR. Page action is for features that available to some but not all pages or websites. If you are making an extension to extract all images from a page and make a slideshow, page action is preferable since not all pages have images. On the other hand, Tab2QR is available for all pages, so browser action is more appropriate. Besides, you can move the Tab2QR button into the dropdown menu to save space, which is not possible if I used page action instead of browser action.