In this example, we'll add an image to poll entries. So we can improve the look of our polls with a leader image. You can add any field to your poll entry.
We want our polls to be somewhat fancier, and supply image next to the question.
Since a poll is a regular content type, you can just edit the Poll entry type.
In the CP Settings -> Sections select the Poll entry type to edit:
You can then add your image to the poll:
When you edit or create a poll now, the UI will look like this and you can add an image:
The twig code to display the image with the poll is obvious,
{% for poll in entry.selectedPoll.all %}
{% image = poll.image.one ?? null %}
{# .. code to display the image and the form .. #}
{% endfor %}