Yeah, I forgot to mention something you should now.
1) Sorta lied, the mega-palette didn't include green, so I needed a additional two palettes for greens. (up to you to use them, but i'll still post them.)
2)Don't replace/use Palette 13, it's dodgy as it only show the first frame so when you walking it looks really stupid...
3)Like half the pallettes are unused, but i've named the pitures what palettes you could replace if you want.
4)If you want to use the palettes all you have to do is open the image in paint (must be paint, Photoshop is crap at doing this for some reason) and paste your OW in, the colours will automatically adjust, then 'save as...' using that method will also index the image so you don't have to fiddle around with stuff (made my life a lot easier.)
5)Nearly all HGSS Ows only fit in the 32x32 frame, so as a general rule I make all OWs this size. To do this (you must do it before you insert the OW or you will have to reinsert it,) Click View>Preferences. Next to save where it says index, select 'All' then change the Width and height to 32x32 and click save.
6)Don't center your OW. Always keep it one pixel from the bottom (but center horizontally.)
Mega-Palette -
http://dl.dropbox.com/u/4875391/PC/0x0A.bmp
Grass 1 -
http://dl.dropbox.com/u/4875391/PC/0x0B.bmp
Grass 2 -
http://dl.dropbox.com/u/4875391/PC/0x09.bmp
Hope that helps :).