Selling physical Habitica goods or patterns is not permitted, but you are welcome to make items for yourself or as free gifts for other people. If you have questions about this, please email Lemoness (firstname.lastname@example.org).
You are encouraged to post photos of your finished projects in your community of choice. There are also several Guilds for crafting such as Knitting and Crocheting, The Seamstress Collective, and others.
The official Habitica blog has a collection of fan art and cosplay costumes. If you would like us to post your Habitica artwork on the official blog, please email email@example.com with the picture and information on how to credit you.