public List<String> getImageMimetypes() {
        return imageMimetypes;
    }
Returns the list of image mimetypes supported by the client. To add or
removed supported mimetypes, the list returned by this function can be
modified.

@return
    The set of image mimetypes supported by the client.
guacamole-common/src/main/java/org/apache/guacamole/protocol/GuacamoleClientInformation.java