Updated : 2021
How to use the Photoshop brushes to create unique custom shapes by using selections / image trace etc tutorial. Brushes can be used as an interesting source of custom shapes.
The brushes in Photoshop are all raster format but can be quickly converted into Photoshop custom shapes.
Goto the toolbar and select the Photoshop brush tool
Select a Photoshop brush for conversion into a custom shape (via the brush presets panel)
Set the color to black via the Photoshop toolbar
Apply single Photoshop brush dab or multiple dabs as required (perhaps apply as a brush stroke)
Select the stroke using the selection tools (magic wand tool, perhaps)
Window menu and paths panel
Right side menu and Make work path
Edit menu and define custom shape
Current custom shapes can now be saved via the custom shapes panel as CSH format file
You can create millions of different brush designs using the brushes available from this site along with the millions that exist on the web. The best conversion from brushes to shapes will be brushes that are fairly hard and sharp with little blurriness. You can then use the paths panel to make a work path for use as a custom shape in Photoshop. Many of the brush sets (on graphicxtras) contain ABR files and PNG files with a single design. Open the PNG file and use the previous method to create a quick Photoshop custom shape from that.
An alternative approach and probably better would be to export the Photoshop brushes design via the pasteboard or via the export of a PNG image or save the artwork to the CC library and re-edited the design in a vector application and use an image trace tool to create a brush path based on the created brush dabs on Photoshop. The vector trace can then be imported into the application via the pasteboard and saved as a new shape.
Start Photoshop
Open a new document
Select brush tool
Set color of the brush to black
Select a brush in the brush presets panel and apply brush strokes
Drag into the libraries panel
Goto Illustrator
Open a new document
Goto the libraries panel
Drag to the Illustrator artboard
Embed
Convert the "Photoshop brush" using the image trace feature (image trace panel ignore white option ON in advanced section)
Select the vector design and expand (object menu and expand)
copy vector artwork
Goto Photoshop
Paste into Photoshop
Select custom shape option
Goto to the direct selection tool and select all the design
edit menu
define custom shape in Photoshop
Personally, I prefer tools such as Corel Trace for the vector trace of artworks and there are also many online vector trace tools (some that you have to pay for) but with a little tidying up and a little care, decent results can be achieved with the trace feature in Adobe Illustrator (though I would love to see a proper overhaul of the tool to include a variety of different ways to do the trace). Another alternative can be found via the Stipplism plugin (for Adobe Illustrator) from Astute Graphics though not particularly a trace tool, the results can be very impressive in creating all kinds of sketched and rough variant traces from Photoshop brushes depending on the symbols etc used to create the trace and then from there the results can be re-imported into Photoshop and then defined as a new custom shape / vector design.