Most of the prepared materials are intended for events or promotions that have defined start & end dates. For example, Petco Foundation includes electronic "toolkits" for their in-store promotions for things like "Be a Foster", "Cat Week", "Helping Heroes" and similar events throughout the year. it makes flyers and social media posts basically cut & paste easy with really professional-looking results.
Specific to Maddie's Fund, there are some very nice graphics for the 25th Anniversary here: https://www.maddiesfund.org/25th-anniversary.htm This can be added to your website. Great looking on t-shirts and such, too, which are available for purchase (see link on above page).
A couple of current events that you might want to review that also have graphics available:
Remember Me Thursday Sept 26th https://remembermethursday.org/
Best Friends "Strut Your Mutt" various dates around the country depending on your city
https://support.bestfriends.org/site/SPageNavigator/landing_page_home.html
sample graphics:
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