Visual hierarchy

Size, contrast, colour and position set the order. A face at high contrast usually wins the first look, then a short run of text, then whatever is left. Where a subject is looking pulls the eye as well, so a face turned towards the text drags attention onto it.

Weak thumbnails have no hierarchy at all: three elements at equal weight, each fighting the others, and at feed size the eye settles on none of them. Decide what the first thing is before you open the design, then make everything else obviously smaller or quieter. Check it at the size it will actually appear.