I'm running it on a Pi3b, and have no problems what so ever,
whats are you running it on?
you could try making sure that the emulator names match that of the images for the system, i had a similar problem when i 1st started using the theme, also i believe this theme is designed for 1080p not sure if you are using a lower resolution that may also be the cause.
i will check my attract mode set up and post the settings i have if that helps?