You can try with https://beta.illustrio.com https://beta.illustrio.com, it's still in beta but I’ve been granted access lately. My experience with it is pretty

You can try with https://beta.illustrio.com https://beta.illustrio.com, it's still in beta but I’ve been granted access lately. My experience with it is pretty close to what you’ve been describing. You can easily search for images, and filters by style (flat, outline, etc) and category. Then you can change the look (customization include color and position of elements), and finally download in the filetype and format you like. From what I understood, the whole library is created with SVGs allowing for manipulation.