OmnicomMediaGroup USA | 11,093 followers on LinkedIn. OmnicomMediaGroup (OMG) is the media services division of Omnicom Group Inc. (NYSE: OMC), the leading global advertising, marketing and corporate communications company, providing services to over 5,000 clients in more than 100 countries. OmnicomMediaGroup includes the full service media networks OMD and PHD as well as a number of specialty media communications companies.