Follow this link to set up an email signature for Gmail here
Gmail signatures will accept images, however it is a requirement that the images are hosted. Hosted either on your Google Drive account or hosted on a webserver like Bluehost.
It makes sense to store it on Google Drive, since it is a great place to store all your business and company logos, images and go to documents.
To host your image on Drive:
– Log in to your Drive account
– Create a new folder, giving it a suitable name
– Previously the folder had to be set to public visibility. However this is no longer required
– Open Gmail, click on the gear cog and choose Settings
– Scroll down to the signature section.
– Click the image icon above the text area to insert an image
– Choose “My Drive” to display the images in your Drive
– Select your company logo or image