This year's event has caused uproar due to protests and the death of three horses.
Gordon Elliott has admitted the image is real and has apologised.
Activists have called for better safety precautions.
A 16-year-old boy was arrested on suspicion of affray.
Crucial Role was injured in a "horrific fall".
"If you can’t let them enjoy themselves without making fun of them, you’re not welcome in Liverpool anymore."
Since 2000, 48 horses have died there.
40 runners will take on 30 fences at Aintree.
Animal Aid said they raised concerns about the horse's health last year.
'ITV has done to racing what Chris Evans did to Top Gear'