JGoombaBuilder is a Java GUI for combining the Goomba emulator (preferably Goomba Paletted from http://kuwanger.altervista.org/gba/goomba) with custom borders, custom palettes, and/or Game Boy ROMs. The border conversion code is based on kuwanger's Append program packaged with Goomba Paletted.
Borders should be 240x160, and can be in any format supported by Java. PNG images are recommended, but partial transparency will be discarded. If there are no transparent pixels in the image, a 160x144 area in the middle will be made transparent automatically, which maintains compatibility with old PNG files made for kuwanger's program.
Palettes can be in raw .pal format. (generated with txt2pal.py or goomba_pal_builder.exe, which are included with Goomba Paletted) or in the .txt format used by goomba_pal_builder.exe.
For borders, palettes and ROMs, you can use the "S" button to sort the list alphabetically, the up and down buttons to move one or more items in the list, and the ? button to show a preview.