Unstock is a good site for generating custom vector SVG logos, icons and illustrations. It's got a lot of controls to generate high-quality images fast, and it's good for anyone who wants to improve their content with some professional-looking imagery. The tool is free, so it's good for books, websites, social media posts and other uses.
Another powerful option is Paint Potion, which generates custom vector illustrations in 30 seconds. It accepts a prompt and style reference, so you can match a client's style exactly. You can upload your own reference images and export illustrations as SVG or PNG. It's good for small teams, agencies and solo designers who want to speed up their workflow.
If you want a more basic, easy-to-use design experience, Illustroke is a good option. It converts text prompts into vector illustrations with more than 40 styles, and the output is scalable and editable. It's got a four-step process to get what you want, which is good for generating website illustrations, logos and icons. The tool also has an optimized SVG converter built in for easy integration.