The Apprentice, What would stop you?

For a modelling competition I need to go out on the high street at
Oxford Circus and sell as many of my photographs as possible to passes
by. Does anyone have any ideas of how I could get people to stop and
buy a photo from me. Any ideas appriciated........ What would stop
you? How have people stopped you in the past? What would make you part
witrh £1? What would be a conversation starter?

This will be on T.V so camera's maybe following me......