In Australia there's very good evidence with respect to the success of their picture warnings. There is an international tobacco control study that measures the impact in different countries. Another example is Thailand. When they increased their size and used pictures in particular, compared to a neighbouring country, Malaysia, which did not, there was an increase in the impact of warnings. Just for those two comparator countries, there's lots of evidence that adding pictures--sometimes combined with size, sometimes not--increases the impact.
The evidence is overwhelming. That's why every year the number of countries that require picture warnings grows, and we see this trend growing.