Here are some helpful tools on changing the Graphics in Ruby. Sapphire, Emerald, FireRed & LeafGreen >>>
1. APE (Known as Advanced Palette Editor)
Description: This tools his helpful if you are trying to change the palette of your tiles in you R/S/E/FR/LG hack.
How To Use:
A. Click "File" and the select "Open ROM"
B. After the ROM is loaded you can either load palettes by searching or typing in a offset.
Download Link: http://www.freewebs.com/darkjagold/Hacking]http://www.freewebs.com/darkjagold/HackingTools/APE.zip
2. Overworld Editor
Description: This tool enables you to to change any of the Overworlds in your R/S/E/FR/LG hack.
How To Use:
A. Click "File" then select, "Open ROM"
B. You can select the OW (OverWorld) by using the top scroller and changing it's movement postions by using the bottom scroller, bit are beneath the main Picture area.
C. You can also import your own Overworlds aswell
D. To actually edit the overworld, just click a color on the right side and the draw as you are using MS Paint.
Download Link:
http://www.freewebs.com/darkjagold/Hackinghttp://www.freewebs.com/darkjagold/HackingTools/overworldEditorRE.zip----
HOPE THIS HELPS!
NOTE TO HACKERS: Make sure you have downloaded WinRAR before downloading these tools.
More to come soon!
-jk-) 
I only started like 10 days ago, and I'm a pretty good mapper! Right now I only hack 3rd gen games, since I can't read Japanese 