When I won the trip to the World Cup final last year, this term came into play. One requirement of the prize was to cooperate with the publicity surrounding the winner. This was a simple matter of sending in a photo to be used (of my choosing & taking), to accompany an article about the trip, which they wanted me to put together from my point of view.
The clause about a "model" would apply if I needed to keep my "dirty little gambling habit" away from friends and family. In my case, it is well known in family circles that I spend my time trying to win money either from Fruit Machines or the internet (and rarely succeeding

) - so no "model" was necessary. Most publicity seems to use a "silhouette" rather than an actual model for those winners who want to remain anonymous.
One reason I was given for the need for this term was to show that the prize had indeed been won by a "player", and not rigged like some of our UK TV phone-in contests

A mere 10K win just gets the usual "mention in dispatches", usually the newsletter or winners list.
None of my casino wins have been big enough to warrant more than this, the biggest being 16K, with a few over 10K. They tend to remark on individual payouts, rather than a longer winning streak, although Palace Group is an exception, winning streaks get a mention too! Nice to know "big brother" is watching your every move, even when playing at 4am