Gumroad also sells tools, scripts, and utilities for artists. Not just art itself.
Example;
https://wzx.gumroad.com/l/lightit?layout=discover&recommended_by=search&_gl=1*sczj9e*_ga*NTc3NjAzMTMxLjE3MTA2MzU1NTg.*_ga_6LJN6D94N6*MTcxMDYzNTU2Ny4xLjEuMTcxMDYzNTU3NC4wLjAuMA..