FlipperVolt is free (for right now.) In order to provide a great experience for as many people as possible, we need to limit the number images you can mark as favorites.
Remember, you can always download any image you like. (In fact, we highly recommend you download the images you really like as we cannot guarantee that any one image will be available again.) If you change the download “Save Action” option in the settings page, you can opt to download-and-hide, download-and-favorite, or download-and-do-nothing when the “J” key is pressed or the floppy-disk icon is clicked.