Most mini games start with referenced colors and style but all mini games start with the same UI template. After that I am free to concept out my I favorite ideas, with some fast painterly block in technique. If the team is happy with the direction, then I can polish them into the final in game art peices.
Most mini games start with reference for colors and style and a UI template to create around. With those in place I can start blocking in a fast and dirty painting, focusing mainly on the UI areas.