One easy way to promote your collection is to have staff take turns selecting 5 books on a theme from your collection, take a photo of them and post it to your social media. If you make it a regular feature, patrons may look for it and find their next great read. Set up a calendar and let different people from throughout your library get a chance to pick their five books.
One display I try to put up every year is a selection of cookbooks for Thanksgiving that contain recipes outside of the usual options. Include vegan, vegetarian, international, and cookbooks for those with special health concerns. This will show off your cookbook collection while giving patrons ideas if they are seeking something unique to serve.
As an example, I have several photos of cookbooks below with a simple fall themed picture behind them. You could add text explaining the theme and have just the first photo or add photos like I did below with each book shown faced out. Let your patrons know that you have a wide variety of cookbooks and give them some out of the box ideas for their holiday celebration.