Currently, you can add a custom image to Okular's stamp tool by entering the image's full path into the combobox. This UI is sub-optimal for the following reasons:
- The typical workflow for selecting images for some use involves a button with text like "choose image" that opens a file chooser; many/most users would never even think of entering a path into the box.
- The user needs to be able to enter a valid file path, which is a challenging task for many/most users, especially if the file or any intervening directories contain spaces or symbols.
- There is no feedback when an invalid path is entered or an image with an unsupported file format is chosen. It just... doesn't work, but the invalid path/file stays there in the combobox.