I feel like more themes for the game would be great for player experience and a way to generate more revenue. I feel like more free themes would be in order, maybe one or two more. Next have some themes you can earn through achievements or challenges with really hard achievements having cool themes. Then of course have themes that players can buy with their scales, but also make it so players can unlock the theme for a certain amount of time if the watch ads. If you really feel like it ad in themes you can permanently unlock with ads, but its understandable if you don't. I believe all ads should be optional and this would be a cool way to implement it. While not the ultimate arbiter of how you do things, there doesn't seem to be much to do with scales and this at the very least seems like an idea.
Under consideration feature