t1gr0u

The plugin allows to change theme (template) on desired dates. 
If you want a Christmas theme automatically on your blog just for 5 days (or more), the plugin will do it for you.
Just enter a start date, an end date , select times and the theme which you want to use, that’s it.
You can have as many combinations as you wish.
A theme for each seasons, halloween theme, christmas theme… or even a day and night theme…
<h3>Admin Panel</h3>
The admin panel will allow to move re-order your theme changes. 
Just remember that, the top is the lowest and the bottom is the highest level. 
So, if you have a theme change (‘theme1’) set for the 23/07 – 01/08 first and theme change (‘theme2’) for the 24/07 – 26/07, and today’s date is 24/07, 
‘theme2’ will be displayed unless you move down ‘theme1’.”
The rules, which you have created, will stay year on year.

WP Change Template

The plugin allows to change theme (template) on desired dates.

rhewlif

Provides a simple sidebar widget to display NASA’s Earth Observatory Image of the Day and/or the RSS feed. Numerous options are available to display the content the way you want, including control on the image width and description.
The widget can also output just the RSS feed, providing links to previous images for up to the last 10 days (maximum available in feed).
Thumbnail images are cached to the plugin folder daily if needed, and the RSS feed is updated hourly.

Earth Observatory IOTD Widget

Provides a widget to display the NASA Earth Observatory's Image of the Day and/or the RSS feed on your sidebar.

WP Change Template vs Earth Observatory IOTD Widget