In this video I show you that you can basically create from any object a Photoshop Brush. For best results the object you want to make a brush of is in black 'n white already. Any color will be in grayscale. Especially when you create your signature brush, make sure the signature is in black on a white paper.
Important: if you want to turn a single object from any photo into a Photoshop brush, you have first to isolate it. (mask it, hiding the background of the original photo)