Outlook 2013 provides a wealth of features as a desktop mail client, including email signatures. This will be a brief overview of how you can add an image to your email signature in the Outlook 2013 desktop client.
Open the Outlook 2013 desktop client.
Click the button labeled 'New Email' in the upper left-hand corner of the main Outlook 2013 window.
From the 'New Email' dialog's Ribbon, click on the option labeled 'Signature' in the 'Include' section.
Select the option labeled 'Signatures...' from the menu.
In the 'Signatures and Stationery' dialog, click the button labeled 'New' located underneath the 'Select signature to edit' section.
Give the new signature an identifying name
Click the 'Insert Image' button, located on the right-hand side of the 'Edit signature' section.
Navigate to the desired image in the file browser window, and click the button labeled 'Insert' located in the lower right-hand corner.
Move/resize the image as desired for your signature.
Optional: In the 'Choose default signature' section, select the signature to be used for new messages and replies/forwarded messages, using the dropdown menu for each option, respectively.
Click the button labeled 'OK' in the lower right-hand corner.