Ok people this is a way to hack pokemon roms using Advance Map, its kinda easy for me since I'm used to it now, but you should get the hang of it!sorry if its a bit long
Ok first go to http://www.studiopokemon.com/wah/It also might work on some other roms then pokemon but i use it for pokemon roms mostly
Now when you get to the site its in a different language so press on a symbol that translates everything to English it should be in the first box called Bievendios!
eg this pic;
After that look down the list of things on the left at the end there should be "Tools" go into that
Now you can find advance map and elite map right at the very top of the list, go advance map (i don't like elite map)
Press unload and download it into a folder or anywhere, it should be in a zip folder, unzip it all!
Now go into the program, click on the picture of the game boy cartridge to load a rom, it should then come up as this(it also explains some things
After your rom has loaded click on "By Header" it should come up with a list of maps hopefully in English!
Now click on any map you want to change, eg; little root
It should come up with a picture of "Littleroot" and as you can see over on the right of the map there is a whole lot of jumbled up pictures click on anything then click on the big map, it should then change it to whatever you chose!
Here is my new "LittleRoot";
Now as you can see there are little tags above the map, first click on movement permission view, which does exactly what the name says, here is a pic to show well most of whats what; The rest of all the movement squares i dont really know, but hover the mouse and look in the left hand corner of the program and it should describe what it does!
Now go to the next one "Events View" I am not going to put a picture on here because its very simple as it is!
You can make the sprites on the page or move them to places where, or even change what they look like!
Now moving onto the next tag, "Wild Pokemon View" which is pretty simple, press create new pokemon for the new map or an old map, then it should come up with something about type and offset for where you meet these pokemon, tick on of the boxes and go through all the things it comes up with!
The next one is really simple, all the map options ITS ALL EASY JUST PLAY AROUND OR EVEN TRY AND MAKE NEW GAMES FROM OLD ONES! WELL I HOPE THIS HELPED! HAPPY HACKING!