The attribute stones is very complicated.
You will need to add new sprite, bmp inside item-pack and item-ground. Then register the new BMP and FRAME.
Then need to adjust the new sprite to be read by client. That is consider the easy part, then you need to code the function for attribute and item3.cfg.
If you are not an advanced level, I advise you not to get ahead of yourself on this. Because the code and guide for this will be hard and long for you to copy and paste.
Furthermore you need another coder to actually paste his codes for everyone :-), Good luck.