My Mobile App uses your mobile friendly website as the basis of your app.
Any changes you make to your website will automatically be reflected in your app. This applies for design changes too.
Therefore, yes, you can change the theme of your app. This is done by changing your website, i.e. outside of My Mobile App, and the app will match whatever changes you make.
To make changes to your Native-Style version of you app, please contact our support team and they can assist in reconfiguring your home screen, and adjusting artworks if required.
If there's something in particular you'd like to see added to your app - please be in touch with your suggestions and feedback!