What is important and in order to produce an interesting essay, is to see your unique perspective and analysis of the elements in the topic. 

It is also important to make sure that your essay is focused and well-argued, regardless of which example/s you choose to analyse. Make sure that you have a clear thesis statement and that your analysis of the elements is supported by specific examples and evidence. Additionally, be sure to engage with any relevant academic literature on the topic to demonstrate your understanding of the subject matter.

Ultimately, the quality of your analysis and argument will be what determines your grade, not necessarily the specific example you choose to focus on. Though a poor example may lead to a weaker essay, and thus a lower mark.

We shall examine how feminist and fashion theories intersect, as both fields concern social norms, power dynamics, and representation. We will discuss one of the main ways feminist and fashion theories relate through analysing gendered norms or expectations in clothing. Many feminist theorists have long argued that gender is a social construct and that dress and adornment significantly shape our understanding of gender. In addition, many say that clothing reinforces negative stereotypes of gender identities and norms, even suppressing one gender over a dominant one. Similarly, we will explore how clothing and style are used to express and subvert gender identities to further the feminist cause.

Although the lecture has yet to come up, I'd encourage you to explore the provided content and continue researching.

The ideas you present to explore Princess Diana's dress are interesting, but there are some challenges. Of course, firstly, you'd need to provide a compelling case that she expressed feminist ideals through her dress. Was she a feminist?

I'm a bit confused about your use of "Power dressing". Power dressing is a term that emerged in the 1980s to describe a style of clothing that was designed to convey authority, confidence, and professionalism, particularly in the workplace. I think you'd need to prove that she dressed overwhelmingly in a way that could be described as ‘Power Dressing’ if you pursue this. Does this need to be the crux of your argument?

You could certainly explore how she dressed during her marriage to Prince Charles v divorce. During marriage it was often a traditional, conservative style appropriate for her role as a royal (future Queen) but this evolved as she became more independent towards the end of her marriage and after her divorce. There is a solid case to present as she began experimenting with bolder, more daring styles. Did this reflect her newfound independence and sense of empowerment? Can you argue that? Did she dress with hidden codes? The iconic black sheep jumper was no coincidence!

Overall - interesting ideas developing. Needs some refinement, but I'm excited by its possibility. 

With that said, including a section in your essay that doesn't directly relate to fashion/your main topic can be acceptable as long as it serves a purpose and helps to contextualise or set the scene for the main subject of your investigation. You need to ensure that the connection between the introductory section and the main discussion on Fashion is clear and logical is vital. 

Tips:

I hope that is helpful. 

Here's an example of how you can reference a film frame within your essay:

Under your image, you would have something like: 

"Fig.x. In the film To Catch a Thief (Hitchcock, 1955), the character played by Cary Grant is seen wearing a mischievous smile as he gazes at the breathtaking French Riviera landscape (Frame 120)."

In your bibliography, you would put something like this if you watched it online:

Hitchcock, A. (1955). To Catch a Thief. Amazon.co.uk: Prime Video. [online] Available at: https://www.amazon.co.uk/gp/video/detail/amzn1.dv.gti.d2a9f67f-8045-98c3-956d-115953971200?autoplay=0&ref_=atv_cf_strg_wb [Accessed 21 May 2023].

Or if it's the film on DVD:

Hitchcock, A. (1955). To Catch a Thief. [DVD]. Place of distribution: United States. Paramount Home Video (Special Collector's Edition) Region 1.

The LEARN Module page has a Harvard Reference Guide for further information. In addition, the Uni library has extra resources, and there is a lot online if you need additional help.