The shocking images were released today by police as the toddler's mum Lauren Coyle and her boyfriend Reece Hitchcott were jailed for 10 years each for causing her death by neglect.
A duvet was then placed over her, meaning she could not properly regulate her body temperature.
At some point during the night of March 22 to 23, she stopped breathing and her heart stopped.
She was taken by ambulance from her home in Lostock Hall, near Preston, but died at hospital.
A post-mortem examination concluded the cause of death was “forcible restraint by ligatures in a facedown position complicated by hyperthermia”.
Coyle, 19, and her 20-year-old boyfriend Reece Hitchcott were found guilty at a trial last month of causing or allowing Ellie May's death and child neglect but were cleared of manslaughter.
Detective Chief Inspector Zoe Russo, of the Force Major Investigation Team, said: “Ellie May was 19 months old at the time of her death, she was a lively and energetic toddler.
“At that time she was living with her Mother Lauren Coyle and her then boyfriend Reece Hitchcott. Ellie-May was in the care of the very people that should have loved, cared and protected her.
“Today at Liverpool Crown Court, Lauren Coyle and Reece Hitchcott were sentenced for causing or allowing the death of Ellie-May by caging and restraining her in her cot which then meant she could not breath properly and sadly subsequently died.
“This case has been very distressing for all parties concerned, particularly the family of Ellie-May. I would like to thank Ellie-May’s Father and Grandparents for the dignity with which they have conducted themselves throughout the investigation and trial.
“I hope the sentence means that they feel some level of justice for the death of Ellie-May has been achieved and my thoughts remain with them.
“My thanks are extended to the wider prosecution team, the expert witnesses, the live witnesses at court and the jury, who at times had to endure some extremely distressing material."
Brett Gerrity, Senior Crown Prosecutor from CPS North West said: “Lauren Coyle and Reece Hitchcott have been jailed today for seriously neglecting Ellie May and causing her death. They denied all responsibility and blamed each other but together CPS and police built a strong case and presented the evidence to the jury that proved they were to blame.
"This was a tragic case in which a young toddler who should have been safe and secure at home needlessly lost her life. I hope today that Ellie May’s loved ones are able to gain some comfort that justice has been served."