Parameters are accessed with C4DAtom::GetParameter()/ C4DAtom::SetParameter(). See Parameter IDs.
Parameter: Name
ID_VS_TAG_NAMEParameter: Image File
ID_VS_TAG_IMAGEParameter: Aspect Ratio
ID_VS_TAG_ASPECTParameter: Base Size
ID_VS_BASE_SIZEParameter: Lock HotSpots
ID_VS_TAG_LOCKParameter: Add
ID_VS_TAG_HOTSPOT_ADDParameter: Remove
ID_VS_TAG_HOTSPOT_REMOVEParameter: Icon
ID_VS_TAG_DYNAMIC_BUTTONParameter: Link
ID_VS_TAG_DYNAMIC_LINKParameter: Command ID
ID_VS_TAG_DYNAMIC_COMMANDParameter: Text
ID_VS_TAG_DYNAMIC_NAMEParameter: Action
ID_VS_TAG_DYNAMIC_ACTION