I was the both the design manager on the MyM team as well as a contributing interaction designer. I dabbled a bit in the visual design but mostly left it those who were just plain awesome. Below is a view our theme creation UI which allows users to upload backgrounds and edit font colors and typefaces. We worked endlessly on making sure the UI was always readable no matter what the choices made by the user. We used contrasting font colors and gloss/shadows to help with this. 

Here is a look at the UI in another theme as well as a look at the conversation window. One interesting feature was the bar at the top of the conversation that reflected the Theme of your contact. We did this so that users would be able to express their creativity by creating a theme that their friends would see while they were chatting with them. 

This is a close up of our Emoticon Studio. We created a UI for creating custom Emoticons and then allowed users to save, edit, and send them between one another. This was another feature focused on self expression for the youth based target market. Ok, it was fun for us adults too :-)