Action Replay on DS
The term Action Replay refers to both the device that allows modification of the way software runs on a gaming system and the "cheat codes" that define how the game rules are modified. The Action Replay device for the DS does not allow you to use pictures or photographs. However, multiple devices that support its codes do allow customization of menus, backgrounds and other elements. Each of these devices has different capabilities, strengths and weaknesses but give you the capability to put any image on your DS.
R4DS
The R4DS (Revolution) series cards are one of the oldest slot-1 flash card systems for the Nintendo DS. In addition to allowing you to play backup images of your personal game library as well as providing home brew software support, the R4DS has full support for Action Replay codes and the ability to turn them on and off selectively without resetting your system. This solution also allows a straightforward drag-and-drop interface for files, including pictures from your computer. On the down side, the R4DS is dated by comparison with other solutions and and requires special steps to convert images into skins.
AceKard DS
Like many other slot-1 flashcards, the AceKard allows you to play game backups. It sports a cleaner interface and greater compatibility than the R4DS in most of its functions, including its capability to import, utilize and apply Action Replay codes to your games. Its skin-creation tools are more robust than R4DS but still lacking in comparison with newer cards. However, the capability to add images to the DS is a simple drag-and-drop affair.
CycloDS
CycloDS is a next-generation slot-1 flashcard with a broad range of uses, including the capability to run backup games, play mp3s and read e-books with minimal effort. It has one of the greatest ranges of Action Replay code support of any current flash card and has regular firmware updates. You can move pictures to this device as easily as with any other choice and you can convert these images into skins or backgrounds with ease. With the advent of the 3DS, this is the only solution that currently supports 3D skins.