What are some alternatives?
When comparing Retrowave Illustration Pack and Interfacer, you can also consider the following products
Stubborn Illustrations - 30 little exciting stories from the startup world
Facebook Design Resources - A collection of free resources made by designers at Facebook
Stories by Freepik - Awesome illustrations for your next project
Freebiesbug - Collection of the best free web design resources.
Illustration Tools - Directory of tools and resources for illustrators
Designer Mill - Collection of Best Free Design Resources