How do I deploy an image to an existing Linode?

First create a new disk from an image, then create a configuration profile for the new disk:

1. Select one of your Linodes (make sure it has enough disk space available to hold your desired Image).
2. Go to the Settings tab of the Linode's menu, then choose Advanced Configurations.
3. Choose Add a Disk, then when the disk drawer opens select Create From Image.
4. Choose an image and disk size, then create the disk.
5. You will be returned to the Advanced Configurations menu. Choose Add a Configuration, choose your new disk from the dropdown menu, then submit the form.
6. Click on the action menu for the new config and select "Boot this config."

You can also boot from the new config just by booting the Linode: you'll be prompted to choose a configuration profile.

@grump

Thanks for this insight @jskobos