The badges are changed with UnLZ-GBA, a tool that edits the sprites in the rom.Im hacking emerald.
How do you change the badge pictures? also is there a tool for editing trainers? and how do you edit the titlescreen?
As for trainers, there is another tool called Advance Trainer, by HackMew.
Henceforth, this isn't the place to ask for these. This thread is directed twards Emulation.
For future reference towards rom hacking and editing, please ask your questions in this thread.