It feels like you and many other commenters have missed the broad general point to focus on the proverbial trees. I am replying to this comment because it is at the top of the HN comments at the time of this reply.
It is a part of computing history that computer scientists at a respected educational institution chose to use a cropped version of a nude Playboy image as part of a test suite for the development of JPEG. Part of that history is that in the 1970s someone felt it was appropriate to openly bring a copy of Playboy into the office and the response to that was to use something from it for an image test suite [1]. You are personally welcome to feel about it however you will.
However, many women are stating that the continued inclusion of a Lena image in test suites and as an important part of computing history makes them feel unwelcomed in tech spaces. As a hypothetical, perhaps you are a straight male. Imagine for a moment that computer science was instead historically dominated by gay men, and that they had decided to use images from gay pornography as part of the JPEG test suite. Suppose that gay men continued to be highly represented within the computer science workforce, and that in order to learn about JPEG compression, you also had to be confronted by those images in a computer science lecture hall in 2023 while surrounded as a straight individual by a room full of gay men. Suppose you hear even one classmate who feels comfortable, in this professional setting, commenting that "they could use some company like that around here" and hearing a few classmates chuckle around that.
Computing and computing literacy are such useful skills today. There are a myriad of tasks where even basic programming literacy would allow you to automate things and make you more efficient in your endeavors. More broadly as a society, we are leveraging machine learning models in so many contexts, and these have been shown to encode the societal biases which were present in their training sets. Representation across all axes of identity allow everyone an equal footing to advance in this technical skillset and also increases the chances that we identify when computing technologies are encoding bias in harmful ways. These women are saying that there are many things which can be done to improve the representation of women within tech spaces, and that removing Lena from curriculums and test suites does zero technical harm while increasing inclusivity. That is the ethical judgement at stake - to what extent do our current practices harm inclusivity and affect the likelihood of encoding harmful biases in the technology we develop now and in the future?
[minor point - if you are a legal stickler, use of the Lena image was also done in infringement of copyright. This is such a non-point in the actual discussion of the campaign, but it seems like a lot of comments basically fall along the line of "this is legal so whatever" and if you want to argue on this perceived technicality, it isn't even correct.]
[1] http://www.lenna.org/pcs_mirror/may_june01.pdf