Street photography - easy for everybody as it does not have to be a busy or a lonely street. Any interesting street should suffice - anything between a mountain road and Fifth Avenue :)

Would this include street art as well? Or is it more of a "road" Photography?

I presume that as long as you show a bit of the street as well then it will fall under this category.

I am suggesting Waves. These don't need to be water waves. They can be light waves, sound waves, heat waves, sine waves, gamma rays or what have you.