During the Sendoso Touch setup process, you'll have the ability to allow your Senders to choose the theme of the gift emails they send.
In step 3 of setting up the Touch, you will see an option to Allow sender to choose theme.
Sendoso Choice Touch set up:
When you check this box, your Senders will be able to select a theme from your Customization Center.
Inventoried Touch set up:
To learn more about how to choose a theme when the send is initiated, check out this article: How do I change the theme of my gift email?