Help with the sprites located in the pokédex of HG/SS

[RookieHacker]

I recently said that I was going to start hacking Soul Silver and I don't have much experience with rom hacking, and let's say I got stuck (again) with the Pokédex editing, but this time I have to replace the graphics of the Pokédex...

On my research I've found that the graphics of the Pokédex are located at a/0/6/8 of the internal files of the game, I checked it with Tinke and yes, the graphics were there, now, I tried to replace the graphics there but once I opened the modified rom, I only noticed the only thing that have changed was the color palette of the graphics, but the original sprites were still there...

I've tried replacing the sprites many times but it never worked, I tried to search a tutorial of how to edit the Pokédex's sprites but I didn't find anything...

If someone knows how can I edit the sprites located at the HG/SS Pokédex, it would be of great help.