You need to allow the Graphic Themes to be transparent or change background colors
Right now it's not possible to change the background color of the theme graphics OR make the theme graphic background editable/transparent.
When layering, this feature becomes useful to create cool effects.
ALSO, you need to allow multiple layers on the timeline. Right now, there's only 4 layers available. Not much room for expansion.
Thanks for writing in. Yes, I think having the ability to modify the opacity of a specific layer would be very handy. That's something we would like to introduce.
I did want to let you know that you can (for most) graphic templates change the color of the background/shape layers. With the title select, open the Edit tab, select the shape layer you want to modify, click on the color swatch.
Let us know if you have any issues accomplishing that.