Brushes can be used to make many cool effect, and you can make them just about any shape that you want.

The first step to making your brush to make the shape that you want. Make a new image with a white bg. Make a new layer on top of your white bg and draw a circle and fill it with black.

Now to make our shape more interesting we are going to give it a little ripple. So, select the Filter menu from the top of your screen

Choose Filter> distort > ripple and use these settings

Your image should now look like this

Select your shape and go to edit> copy.

Now make a new image making sure that your background is Transparent! If it isn't transparent your brush will not work!

Past your shape into your new image

Press Ctrl and A to select all of your image, or just manually select it with your selection tools.

Now go to edit> define brush

 

Name it whatever you want and press OK

Now select your paint brush tools and you will notice a new menu appears at the top of your screen

 

From this new menu click on the triangle to open to the brush selection menu Scroll down to the bottom of the list to find your brush!

Select a color and start drawing :) You make many cool things with different shapes, you'll just have to experiment!