Usually, my Sims are based on other Sims (either gallery or townie) and I typically had a photo of an actual person to use as a reference, either from a stock photography website, Flickr, or an online retailer.
Very few of my "from scratch" Sims have turned out well, and I often delete them later on. Sometimes, I work on them over time to get a better result.
The Sims that are based on real people sometimes have several versions.
Take the Sims based on actress Amber Marshall. I've got four versions. Two are my own attempts (some dating back to when I started playing the game in 2018-2019), one is a Gallery Sim based on her best-known role, Amy Fleming from Heartland. A fourth is technically her sister. The two attempts I personally did are named Amber and Emma (which was a character she played in a TV movie about a year ago) The Gallery Sim I downloaded retains the "Amy Fleming" name in every save (despite usually being aged up to an adult, as opposed to a teen from the original Gallery version); and Nicole (based on a role she played in an awful SyFy channel TV movie; Mutant World) was actually made in CAS using the Gallery Amy's genetics, and in most saves, is usually her older sister when I have Amy aged as a young adult (Nicole is usually an adult in those cases).
I recently overhauled a Sim based on a woman (an actual cowgirl, might I add) I found on Getty Images. Because the watermarks bugged me, I'd often run the photos on Getty Images through a search engine to see where they were used. Turns out, a book author had used her photo to represent a character in one of the books. The old version gained the book character's name and background (traits); while still retaining the clothing.
One time, I did a save without checking "skip if same name" in MCCC's population settings when using Gallery Sims. I ended up, and I'm not kidding, 5 different versions of my Simself with different names, ages, and spouses.
