Yes, you can! When you are creating a Campaign, you will see at the bottom of the touch the option to insert a signature. If you haven’t already, you can create your signature by selecting the "Create" button. From here, you can re-create or create your signature and insert images and links to it.
Feel free to copy and paste text into Signature creation box. (When pasting in the signature box, one must right click and hit paste. Do not use keyboard shortcuts)
If you plan on adding an image to your signature it MUST be added using the 'Image' button. This image will need to be hosted on a site such such as IMGUR.
Save the image in your computer> go to https://imgur.com/upload and upload your image > once it is uploaded right click on it and 'Open image in new tab'
From the new tab, copy the URL
Click on the signature's image button> paste the URL > Hit Ok.
Resize the image to your liking using the corners or the dimensions box> Then Save.
Once you have created your signature, you can choose to have your signature included for each touch by toggling the "Include Campaigns Signature" button to the right.