Hello.

If I've understood you correctly, you would like to have a one big bitmap image which would be automatically split by the TImageList during its addition process. As far as I know, that is not possible. TImageList works in an opposite way. It merges all added bitmaps into one big bitmap not visible for us. So you have two choices:
- split your big bitmap into the tiles which you want and add them one by one into TImageList.
- write own TImageList which will be keeping a big bitmap into memory and will have a function to return a TImage object with given index.