Modern 1 - a beautifully simple arch form.
Modern 2 - a flipped version of Modern 1.
Modern 3 - a flat-sided oval shape.
Modern 4 - a simple rectangle with rounded corners.
Modern 5 - a simple rectangle with two rounded corners and two square corners.
Modern 6 - a clean-lined rectangle with one curved corner (two curved corners on the horizontal version).
Modern 7 - a minimal circular aperture to frame the most important part of your image.