Please don't perpetuate this myth that royalty free is copyright free. It isn't. People have had to pay huge fines for not understanding this very basic thing. 'Creative Commons' is probably the word you're looking for. To understand the term 'royalty-free' you might want to read the article below, which explains the consequences of not understanding it. You still need to buy a licence but you don't have to keep paying royalties for every new use. https://medium.com/illumination-curated/this-medium-writer-got-a-1000-legal-demand-from-getty-images-113cfa9fb480