Its my first tutorial here but i hope that u will learn sth using it.
lets start
1. at first u have to choose image which u want to use as brush
i choosed star but u can choose whatever u want
2. now we have to cut our image using Polygonal Lasso Tool
3. copy cutted image into new layer. If u want u can modify it. (in my case a shadow)
if u r done hide background. layers should looks like on screen below.
4. now we almost done. We have to save our brush. Go to edit menu and define brush preset (Edit/Define Brush Preset...).
5. Name your brush
6. and w00t? we have our custom brush.
7. enjoy with using it