Elemental Master: Heroes Assemble

The developers describe how their game uses AI generated content like this:

"Generative AI tools were used during development to assist in creating a portion of the art, background assets, and UI icons. All AI-generated content was reviewed and manually refined by our team."

Required on Steam store pages since 2024. It covers content that ships in the game, on its store page or in its marketing — Valve does not require a disclosure for AI tools used during development, so this says nothing either way about how the game was made. Check it on Steam.