Yes, having a sitemap is a good practice. A sitemap is a file (or a path) where all your website URLs will be listed to tell Google and other search engines about the structure of your site content.
Search engine web crawlers like Googlebot read this file to more intelligently crawl your site.
All Pixpa website has dynamic sitemap and is available at /sitemap.xml
And if you have connected your custom domain (http://www.yourdomain.com), then your sitemap is available at http://www.yourdomain.com/sitemap.xml