With back-lit arcade buttons being more and more commonplace these days, I feel there’s a lot of potential for themed buttons. These wouldn’t be used for the primary play buttons, they are intended for secondary buttons like player select and menu. The ones for Street Fighter above are normal buttons with a teardrop-shaped mount.
I have a few others in mind for Pac-Man and Donkey Kong, may share those down the line.
Unrelated: here are some new posts I buried that you may not have seen. Here are some updated posts.