The Lenna image isn't whimsical, it's a cropped nude photo. The people against it don't want image processing to be boring, they want it to be more inclusive. There are hundreds of other whimsical examples that would not be alienating to a good chunk of women.
Most women don't care about this at all. It's way, way down the bottom of the list of sexist bullshit in this industry. Complaining about it is more performative than anything. It's a way to pretend you're doing something for women.
Can confirm, I know a woman who works on image and video compression and she doesn't think Lena is a problem. "It's a pretty woman. What's not to like?"
Note that video compression has "foreman", of the opposite gender, and the angry mob hasn't gone after that one.
