Are there particular people you are wanting to respond, that have not?
Could you list who has sent their pic in already, maybe a few think they have sent it but have not.
If they have sent you a pic but it's not good enough for you to use, could you say that also?
Why scrap the idea if only a few have responded? Is it just to much work for three or four people?
I ask because I would love to be in this painting, I mean WOW my mug included with the Duke's!! what else could anyone want?