Undraw

Katerina Limpitsouni has created a library of amazing and customizable MIT licenced illustrations. They’re free and there’s no need for attribution either.
Her whimsical and fun illustrations are also SVG — scalable at any size without losing any of the quality.

Freepik

Freepik boasts over 800,000 free illustration vectors. There’s everything to choose from. You need animals? What about silhouettes? You’ll find it on Freepik.

Pixabay

Pixabay is another image search engine with a ton of free vectors up for grabs. Pixabay also aggregates images from other free websites, making their collection even bigger.

Vector Stock

Vector Stock is home to over 200,000 free vector images. You can sort them by latest uploads or by trending vectors. As with the other sites, the formats include: AI, EPS, PDF and JPG. All free, all yours. However, the vectors are for personal use only, which is a bit of a limitation for freelance designers.

Flaticon

If you want access to over a million vector icons then Flaticon’s your best bet. It has collections grouped into packs, for easy browsing.
There’s the whole gamut of icons: strategy and management, friendship, ecommerce, marketing and SEO… you name it, Flaticon’s got it.

Reference Blog
https://www.gomahamaya.com/vector-illustrations-images/