Blog post image

Hi, ON my home page http://www.bsab.co.uk/Dev2017/ I am showing my posts with an excerpt and featured image if available. I have added a post which is simply an image which is a poster for an event so instead of showing the image just as a featured image for this post on the home page, I'd like to show just the poster, as just showing it as a featured image on home page makes the image unreadable. Thanks