Can you find one of your images?

One of challenges I have as a photographer, is to find older photos, and even more hard, for somebody else to find one of them in a pile with decades of images. Adding lots of video to the media archive makes it even worse.  

For example, I would like to find an image or a video-clip with a horse on the beach.

Today, all my digital media resides on several computers in my home, and I manage photos, videos and sound in different applications. The workflow is not very much automated and it takes a lot of time to add additional information to the media-files. 

The solution to manage digital assets in form of photos, videos, sound & music should be something like:  

 - Access everywhere / mobile-first
 - Easy and fast to use   
 - Scalable enough for a few users sharing the same content
 - Have a long-term flexibility
 - No vendor lock-in of data
 - Manage privacy for sensitive media
 - Reasonable cost  

The existing applications I use, (Aperture, Final Cut and Logic Pro), doesn’t fulfil these requirements for all media files, except reasonable cost. There are Digital Asset Management systems on the market, but they are very expensive. Vendor lock-in is the main reason for me, not to use Adobe, Apple or Google-services. 

So, if developing a small DAM solution to fulfil the above requirements, how would a high-level architecture look like?