UI elements should be easy to understand. If I'm looking for the settings button I'm gonna look for a wrench/gear looking icon. There was this one app I played where it had most of the UI in the middle. One of the icons was a gear, but it was for customizing your vehicle. The pause button was a wrench tucked away in the corner. I would always hit the wrong button and go to the customize screen instead of the options. This was super annoying. So make sure to use recognizable icons.
|Which icon is more recognizable?|
Layout and Consistency
A messy interface can quickly confuse users. Also keep buttons and there positions consistent. If you have a back button at the bottom of the screen in your menus, keep it at the bottom all the time. It shouldn't shift around.
I updated the menu in an app I've been working on. (I will be showing more of this app soon, particularly the dynamic shadows). The old menu looked cool but was too distracting. I also hadn't finished the icons at the bottom. The new menu is very simplistic.
The middle button on the bottom shows the controls.
|Different control scheme icons|
All of this new menu was made in Inkscape. Hopefully this will help you with your UI design.