I'm not a lawyer, but the terms of use say:

You will retain ownership of such User Submitted Materials, and you grant us and our designees a worldwide, non-exclusive, transferable, royalty-free, perpetual irrevocable right and license, with right of sublicense (through multiple tiers), to use, reproduce, distribute (through multiple tiers), create derivative works of and publicly display such User Submitted Materials solely in connection with the production or provision of any product or service you request or to show you how your User Submitted Materials would appear in our products or services.

Key points:

1. The grant is perpetual and irrevocable.
2. They can do two things with this:
   1. "Produce or provision" a product or service you request, or
   2. Show you how your materials would appear in their products.

A promotional email showing how your materials would appear to be exactly this last thing. It seems a little sleazy to me that they do this with deleted images, but, uh, that's the first bit for you.

So, they don't own your photos, but you've given them the right to do this specific thing forever.

From a privacy point of view, there is some consolation, because the specific rights you've given are limited to showing you how your photographs would look. You haven't authorized them to, for example, use the photographs as examples for other people or the public at large. There's still the risk of a data breach or something like that, but you have that risk anyway whenever you have digital artifacts on a system which isn't powered off and in a safe at the bottom of the ocean.