The Main Screen (start screen) of Rune Master was one I tackled for UI. I'm finding for myself that designing the overall appearance is comfortable, but when it comes down to the actual parts, my designs for some are too cartoony for the client.
This might be partly because I was thinking of keeping the designs simple for readability, which lead to simple designs using silhouettes. Version 2 turned out a bit better, when we decided to theme the buttons towards Aztecs and Mayans with a Mexican clothing color palette.
A week after that though, that decision got turned again by the client, to something more rendered instead.
In the end, the UI elements were redone by the other artists in the team, so I could update the illustrations.
Rune Master is an upcoming puzzle game to be made by White Box Gaming.