I know the theme is more image oriented but I found it also worked very well for what I wanted.

Cheers

We've released an update to Suburbia and that's why you see the grey boxes. The box appears when the post doesn't have a featured image nor images in the content.

The reason we updated the theme is that we find the theme is used by majority of users as portfolio sites where they exhibit images and we think the theme look best with having an image that represents each post like you see in here.

The placeholder (the grey box with the title) is a kind of reminder for users to add an image to each post to get the best look of the theme. It also intends to keep the consistency when some posts have featured images.

If you don't want to have the grey boxes nor images, you can hide them with CSS if you have Custom Design upgrade. The code below will hide the grey box as well as featured images.

.featured-image {
display: none;
}

I want the previous behaviour, How can I get it back
PS: I have not changed any setting