Something else.
Nobody is gonna click on anything that doesn't interest them, that doesn't appeal to their own needs or that doesn't awaken their curiosity. We've all experienced clickbait as well.
So my guess would be:
1. A half decent domain name that a potential domain investor or end user would want would be the single most important part of it. If it has an image or not might matter if it is a brandable name.
2. An advert put in front of domain investors and end users, as opposed to random people that don't care about your domain name.
In summary... a good domain name in the right place for exposure.
I do use images a lot but have been contacted by buyers who haven't seen my advert in many cases. They already know what they want.