Stars are not always placed above the crest, some clubs decided to go in a less traditional route and placed the stars within their crests. Some are symbolic, some are commemorative, but some become a problem.
Aston Villa is a good opportunity to touch upon England, a country where clubs don't have the culture of placing commemorative stars over their crest. Nottingham Forest does have 2 stars for their UCL titles, and Aston Villa placed a discrete star within in crest to also represent its continental title.
Chapecoense from Brazil also has a discrete star within its crest, place right inside the letter "F". This star is symbolic in remembrance of the victims of the fatal plane crash suffered by the club in 2016. The star above their crest is for the Copa Sudamericana title and it is white to represent eternal peace for the clubs heroes.
Cruz Azul, from the Mexican capital, had a star inside it's crest for every national title but a rebrand in 2022 got rid of them possibly anticipating an issue of overcapacity. Not having enough space is a (good) problem that many clubs in Latin America have found themselves with, like Junior for example who decided to get rid of all its stars all together. The decision came at an odd time right when the club had won its 10th title, a significant number that the fans wanted so badly to reach.
Lastly, and more famously, Boca Juniors used to add a star within it's crest for every official tournament its ever won. In the 2010's this became a real problem when the title count got into the 50s. Manufacturers literally were faced with the decision to either cap the number of stars or make them so small they would not be properly visible. Nike stopped adding stars at 52, while Adidas today puts 50 stars.
In 2020 Boca Juniors won the Copa Diego Armando Maradona, which also happened to be the clubs 70th title, and added a symbolic star above the crest with the number 70 within it. This only lasted 1 season but it has been proposed to maintain that star and just update the number within it. Other proposals have been made as well but a Permanente solution has yet to be found.