@Keet
A picture of a wheelchair would probably come a lot closer to the story arc.
Not really; the handcuff are central to the story and associated with both the main and main secondary characters, whereas Wendy (the wheelchair user) is a slightly less significant character than Carole (to the story, even though she shaped Carole's life); also, either a pictured wheelchair wouldn't represent Jeeves (the name for the wheelchair) correctly, or prospective readers wouldn't recognise it as a wheelchair, taking it more as a hi-tech torture device or a starship helm station. The picture is very plain, even stark, but I don't think it would be improved with people in it; showing Carole or Brenda in handcuffs would give an incorrect impression unless Wendy is also pictured, which would shift emphasis to the wheelchair whereas it's the handcuffs that shaped Brenda's life. The only scene that could work would be Carole and Brenda on holiday, but I'm not sure if that even occurred; I may be conflating it with scenes from Hat Trick or The Bet.
ETA: Actually, I'm not sure even that Jeeves was mobile, certainly not any of the early versions; Wendy couldn't take sitting in a normal wheelchair for very long, and I think that it was only mentioned once in the story that she was put in a chair, for a shopping trip. Her life was spent reclining in Jeeves, a sort of high-tech dentist's chair thing.