To transfer pictures files saved on your system, use
LL.LlDefineVariableExt ('Picture', <data path>, LL_DRAWING);
Graphics in the memory (only for BMP, EMF) are transferred with the API LlDefineVariableExtHandle(). For example, to display the graphic as a bitmap or metafile, use the following call:
LL.LlDefineVariableExtHandle('Picture', BufferImage.picture.bitmap.handle, LL_DRAWING_HBITMAP);
or
LL.LlDefineVariableExtHandle('Picture', BufferImage.picture.metafile.handle, LL_DRAWING_HEMETA);