Here are some other awesome products that can boost your digital art!
Kyle T. Webster is a very talented illustrator who has created some wonderful custom brushes for Photoshop.
He offers a wide variety of brushes that simulate natural media, such as pencils, oils, impasto paint, pastels, or even watercolors.
His brush packs will inspire you, and bring new life to your digital work! They are all really fun to use, and very affordable!
Roman Melentyev is an artist who specializes in custom brushes and design tools for Photoshop.
He offers various effects brushes such as shadows, lights, and flames, and drawing brushes such as digital inks, pencils, and airbrushes.
Check these out, along with other awesome tools, at the Creative Market!
AD Brutus Symmetry
Working with symmetry is a lot of fun, and can help you explore design ideas very quickly.
Alex Dukal has created a very cool Photoshop CC+ panel that lets you quickly flip and mirror sections of your drawing! Check it out at the Creative Market.