Is it possible to add a custom field that can consist of a an image, which can be linked?
For example, if an event has sponsors, it would be great to have a custom field, where an image could be uploaded (or chosen from Media Library) and have that image linked to a specific URL for that sponsor.
The closest you can get to this with our Additional fields is to use a text field to paste in a URL to an image and use that. Alternatively you could use a plugin like http://www.advancedcustomfields.com/ which I would highly recommend for custom fields. ACF offers an image field which you can attach to just events and select an image that way. Then, you would just need to modify your event templates to display the image but it’s very easy to do. I can provide an example if need be.