The theme determining the look and feel of the Agent Application's content can be passed as a parameter in the access URL. For example:
http://10.90.18.138:8080/agent-app/?accountId=12345678?appkey=9ad59989-1b45-48d7-9607-763349b3e22f&theme=aristo

If the theme comes from a source other than the default, the absolute path to the folder containing the theme files needs to be passed. For example:
http://10.90.18.138:8080/agent-app/?accountId=12345678?appkey=9ad59989-1b45-48d7-9607-763349b3e22f&theme=http://10.90.18.72:8080/agent-app/jquery/css/aristo