How to change Work In PRogress Thread Place Holder Image?

Sorry if this had been ask before.
It is driving me nuts, is there a way to change the image that appear in the side of your thread in Work In Progress.
I want to change the place holder image in my thread to something better but I don’t know how.
Is it possible to do so?


The forum software uses the first attachment in your parent post of the thread to generate the thumbnail. Edit that post and change that first attachment and you should be good to go.