​Remover fundo:

https://www.remove.bg/pt-br

Remover fundo de vídeo:

https://www.unscreen.com/

Ícones:

https://www.flaticon.com

Mockup : 

Imagens

https://br.freepik.com

https://unsplash.com

Ilustrações

https://www.manypixels.co/gallery/?color=161616&pa...