Bigger image size table visualization

We need to have a dashboard for each person, with each individual results of the person, and we need the person's picture.

We can do that now, but the thumbnail is limited to 30px size (see [Discourse thread](https://discourse.metabase.com/t/image-thumbnail-size/6308))

We would like to have a feature that lets you choose the size of the thumbnail on the dashboard.

A simpler solution would be just make the thumbnail size 200px by default.

This feature is essential to our client and if we don't find a solution, we will have to abandon Metabase.


:arrow_down: Please click the :+1: reaction instead of leaving a `+1` or `update?` comment

Review the dashboard image-thumbnail behavior and the linked Discourse thread first. Clarify whether completion means a configurable thumbnail size or a 200px default, then verify the resulting dashboard presentation against the requested person-picture use case.

Written by the indexing model from the issue text.