Iconscout - Design Resource Marketplace.
Control Illustrations - 108 free flat illustrations with customizable characters
Office Club Illustration pack - Whether you’re creating a website or mobile app, showcasing a portfolio, publishing a blog, or an e-commerce store — Office Club’s 100 illustrations and designed art directions help you create the best possible products.
Free illustrations - Find free to use illustrations & vectors
Craftwork - A collection of User Interface resources made by Craftwork
Struct Illustrations - Create your own unique story with editable illustrations