Here's a long list, in my note, that I jot down from the last JamStack event.. (some time ago.. em..) let's post it here for everyone's reference. I'll also look up their link and added it here, and so here we go.

• Adobe Experience Manager (business.adobe.com/sea/products/experience-..) they have both content management system, and digital asset management. Hence picked your use-case. The latter is more on managing assets that was generated in the studio/department. e.g Game Development Assets.
• Contentful (contentful.com) API First content platform
• Craft (craftcms.com) - Free forever for Solo
• Dato (datocms.com) - the most complete, user-friendly and performant Headless CMS
• Drupal (drupal.org) proudly open source tool for digital experience platform (DXP) on the web. Been a long time.
• Forestry (forestry.io) - Git based CMS .. a fundamentally different concept
• Ghost (ghost.org) - Ghost is a powerful app for new-media creators to publish, share, and grow a business around their content. It comes with modern tools to build a website, publish content, send newsletters & offer paid subscriptions to members. (Paid solutions)
• Kentico (kentico.com) - Kentico is no longer just a content management system. It is a strong vendor brand, a caring employer and a global company with two fully fledged products—Kontent and Xperience.
• Magnolia (magnolia-cms.com) - claims as the fastest way to launch digital experience, my personal view that it's like the alternative to Adobe solutions.
• Netlify CMS (netlifycms.org) - git-based cms for static site generators. I think possibly a fit to mix & match well with JS stack development.
• Prismic (prismic.io) I think they are quite promising too, when matching with Jamstack development
• Sanity (sanity.io) - unified content platform that powers better digital experiences, and it comes in a NPM package.
• Sitecore (sitecore.com) - solutions for digital experiences. more like an off-the-shelves product.
• SquareSpace (squarespace.com) that's more like a range of product that build digital presences
• Strapi (strapi.io) the open source headless CMS.. and 100% in Javascript. also the one that I actually use it in my project.
• Typos3 (typo3.org) the professional, flexible content management system
• Umbraco (umbraco.com) - the flexible open-source .NET (ASP.NET Core) CMS probably.. for another camp on the MS .NET technology.
• Webflow (webflow.com/cms) - content management for building website
• Weebly (weebly.com) - leans towards the website building.
• Wix (wix.com) - towards building the website
• WordPress & WordPress Headless (wordpress.com) - that's possible to use WordPress as headless CMS to provide API , act as data source for front-end application