Icon and vector marketplaces like Iconfinder (where I work) are making well-designed vector icons an inexpensive and readily available resource for web and print designers. Thousands of high-quality premium icon sets and hundreds of great free sets are available. Every icon set submitted to Iconfinder is reviewed and evaluated for potential appeal to our website users and for potential commercial value as premium icons. When reviewing icon sets submitted to the website, we have a responsibility to our designers and to our customers to make sure all premium icons on the website are of the highest possible quality.
Link: https://www.smashingmagazine.com/2016/05/easy-steps-to-better-logo-design/