You cannot make a trapezoid in EA UI but you can use css transform to change the shape of a rectangle.
I mean, I need it for a HTML5 banner, so it should be done inside EA... Is that possible?
Check out my star wars sample and the code. You can modify it as you need. this was made in a previous version. I have not tested it in EA 2015 but I would expext it would still work. Of course I do not know what kind of animation you want to do so this might be completely not what you want.