The 'Danny Phantom' icon is used to bypass nintnedo's firmware 'fix' that blocks flashcards (on DSi's).
Since DSLite/Phat don't have upgradable firmware - the acekard 'Danny Phantom Fix' isn't need - & so the normal ak icon is shown on those
UNLESS Acekard brings out a version of the 1.4 firmware fix that allows you to 'transplant' a game icon of your choice into the fix - there's no way of changing 'Danny Phantom'
1. Danny Phantom is there to make the DSi think it's an actual game.
2. Different games use slightly different algorithms (i don't think i used the right term) for each game. Because of this, the AK 1.4 updater would need to be modified for each and every game.
This shows why an actual game icon is needed, and what data is involved. You could take the update file and transplant a different game's data/icon into it. Other flash carts and such use different icons, for example a fishing game, game and watch collection (which is the example in that guide), and roller coaster tycoon.
The problem is if something doesn't work you'll probably have a bricked acekard on your hands, so it'd make home development of a changer quite risky, and hard, since you'd need multiple cards in order to learn from your mistakes.