1. `aria-label` should be removed to prevent duplication, screenreaders will announce the alt attribute.
2. I would like to add `title="View {{ username }} profile"` to the `<a>` as a help-tag that describes the purpose of the link.
3. a `&s=20` parameter should be added to the gravatar src call, it will give us a more optimized image (and not the default 220x220 image), then we can remove the `width` and `height` attribute as well.
4. that `<img>` will generate a HTML validation error, it requires a `src`-attribute. Maybe it's better to create a js-function that creates that element. something like this maybe :) 
`<noscript class="js-image" data-alt="{{ username }}" data-src="{{ contributor.user.get_profile().gravatar }}">{{ username }}</noscript>`