The evidence cited here (posters, leaflets, etc.) provides evidence that you are producing marketing materials, but doesn't demonstrate that they are effective.  To do that, you need instead to show some analysis of your marketing methods (numbers of attendees to events, hits on website, enquiries, etc.)

There are ever increasing ways of communicating and marketing (once you start with social media alone, where do you stop...? blogs, facebook, twitter, flickr, are just for starters).  It might look impressive to be able to show evidence that you tweet and blog, as well as producing newsletters, leaflets, posters, press releases etc.  But it would be much more impressive to show that:

• you've analysed the most appropriate communication methods for different  types of communication
• you've written things in different styles to appeal to different audiences
• you've tested or got feedback on your communications and improved them as a result if necessary
• you've analysed their effectiveness in doing what you wanted them to do (e.g. raise your profile with certain stakeholders or bring in people to an event)

Problem is that some of this may not be documented at the moment - so this may well result in a lot of work for people.