Configuring your site to enable editing in a multiple site binding scenario
Since the ImageVault instance default configuration only enables editing from the Episerver site URL you need to perform the following steps to enable editing from other base URLs. The binding protocols currently supported in this scenario is http and https.
Add the desired binding(s) to your IIS site
An example from TechNet on how to do this can be found in this article.
Verify Default media URL base value
Since the media URLs are generated with the help of the URL stated in the appSettings section of imagevault.client.config found in the root folder of the Episerver site, you need to verify that the defaultMediaUrlBase is set to use a relative URL and not an absolute URL.
<appSettings> ... <add key="defaultMediaUrlBase" value="/ImageVault"/> ... </appSettings>
If you needed to change from an absolute URL to a relative URL above, make note that images already inserted into Episerver HTML Editor properties will have absolute URL references. If you experience problems regarding this, the only solution is to re-insert those images into the editor after changing the appSettings value to a relative URL.