If I were you I would combine two theories and enlarge my work: cultural and greimás' semiotic . Both of them will provide you elements to analyse beauty and fashion advertisements. Using them you can also analyse the imaginareis behind beauty and its meannings among different cultures.
Also, there is the area of Visual Communication which could help your study—-how do we perceive Color in various cultures? What about headwear in various climes & cultures? Doesn’t Fashion also relate to Body Types? And the political aspects of how by whom clothes are constructed?
Lots of areas to explore here. The politics of clothing are considered an Ethics issue by some, & Ethics is an area of Comm. Studies too.