Strangely I had considered writing a story along these lines....
Basic premise in the 1950's & 60's shopkeepers used to make their own mannakins asking a female family member to hold a pose whilst plaster of paris dried.
I was thinking that perhaps a beatiful 18 year old niece could volunteer for this task at her uncle's shop. She doesn't have the stamina to stand upright for the length of time it takes the plaster to dry so her aunt lies her back on a table whilst her uncle manouvres a plank of wood under her socked feet with a spirit level so the finished mannakin won't be unstable.
She falls asleep and is awoken by the sensation of cool air on her feet as her socks are slowly removed. Stirring slightly a finger is pressed against her lips and she remembers her task, somehow she knows the people in the room are not her aunt and uncle....
As a feather explores her toes she grits her teeth, screaming would ruin the plaster model she is trapped in, her torments smile and begin to use their fingers on her bare arches keeping their administrations just below the amount sufficient to push their victim into moving....
Didn't actually mean to stary writing a story but there you go
Gromets plaza is a great site for mannequin , stuck, bondage and body cast stories and pics. You might be able to adapt some of the stories and add tickling in for your own purposes hope that helps.