Customising the Featured Posts Slider

I’ve just installed Customizr onto my blog (though have yet to make it live) and have begun playing with the settings. I’m stuck on the ‘featured posts’ slider. How can I make the slider feature posts that don’t have a featured image, or an image in their content? Some of my posts are entirely text-based, and lack any images at all. It is my understanding that the front page slider will only show posts with a featured image or with images in their content. Can this be overridden? Thanks for any and all help.