Cannot get modular images to load

This should be simple. Here is my TWIG:
<img src="{{['thumbnail.png'] }}">

The image does not load.

I get this:
<img src="&lt;img src=" user="" pages="" 02.home_mod="" _437y="" thumbnail.png"="">

Nevermind. I’ve worked on this for hours, and as soon as I post this, I figure it out.

I should have had:
{{['thumbnail.png'] }}

I was adding more than what was necessary.

The TWIG that I am using looks more like this now:
{{[page.header.thumbnail] }}

and I’ve reduced it to:
{{ media[header.thumbnail] }}