I think I figured out how to edit the PokeDex world map!
You know how in Emerald, the world map tileset number for Unlz is 245? Well, I found a second tileset resembling the worldmap! The second tileset number for Unlz is 328. I'll try editing it later to see if I'm correct.
EDIT: For some reason I found a 3rd map tileset at 330 (Unlz).
EDIT: I SUCCESSFULLY CHANGED THE POKEDEX MAP!!!
The only tools I had to use was UnlzGBA, and NTME. And no, that image is not fake. I just wanted to make a simple looking map just to see if it actually works.
EDIT: The Unlz number for the Pokedex tilemap is 328 (Emerald). I still don't know what the 330 tilemap is for. And yes, it's in 4BPP.
This is what I did:
1. Open up Unlz, go to 328, 256 Color mode, exported the tileset.
2. Open up Paint, and then pasted my tileset into it (and since Unlz indexes the exported file, the colors are correct)
3. With NTME, make a tilemap with your indexed tileset, save as .raw
4. Back to Unlz, import the new tileset: http://img6.imageshack.us/img6/2637/newtilemap.png
(You don't have to find a new offset, only if it's too big).
5. Click 'Next', now do Load Raw, and select the tilemap you made with NTME. I put in a free offset just in case.
6. Now with VBA, go to your Pokedex, select any random Pokemon, and look at it's "AREA". This is what it should look like: http://img6.imageshack.us/img6/7843/finallyj.png