For research, I looked into existing games that are drawing or mental health related - specifically for children rather than adults. There were a few that already used the idea of a drawing coming to life, so it gave me a good understanding of how I could incorporate it into a game. All of the examples use bright colours, and the aesthetic is typically cartoon-like. I like the freedom that the player has to create and express.
http://www.lucydoesart.co.uk/games.html
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https://www.breezecreative.com/single-post/drawing-game-that-comes-to-life