Add a "Switch to ClassicPress" graphic to the brand assets page.

[johnalarcon]

Per Slack convo, add the following image(s) to the official brand assets page.

[nylen]

This one too:

[johnalarcon]

Noting that these images are not standard banner sizes – the first one is actually sized for the WP plugin repo. No opinion on it either way, just linking a page that contains common dimensions.