Defining ontologies within the multimedia domain still remains a challenging task, due to the complexity of multimedia data and the related associated knowledge. In this paper, we propose: i) a novel multimedia ontology model that combine both low level descriptors and high level semantic concepts; ii) an automatic construction of ontologies using the Flickrweb services, that provide images, tags, keywords and sometimes useful annotation describing both the content of an image and personal interesting information. Eventually, we describe an example of automatic ontology construction in a specific domain.