As you can see in this example, which I created on Codepen, some of the data don’t have an image and whenever there’s no image, a place holder image is shown:
I don’t think handlebars allows anything beyond checking value/existence of variables in if template blocks.
If you want to do more complicated things, you’ll generally want to do that in the template data before you run it through the template. In your case, do the “questionmark” check in JavaScript, then put that result in your template data as something like data.noQuestionMark. Then in the template use