To expand:
>dump content (images, notes, quotes, names of movies)
The images I would keep in relevant logs/wikis, or a timestamped/datetree journal (in it's own file, a header, or a subheader - whatever's more suitable/comfortable). I mostly save images for fun and logging purposes though. The notes I would keep under a (tagged) header that it belongs too, or in the datetree diary if it's personal. Same with the quotes. I keep names of movies I should watch under a (tagged) 'media' header in my tasks.org file (my other org files are wiki.org and archive.org, fwiw).
>tag each item with multiple tags ("book" "completed" "5 stars")
Tags are a built-in feature, but for the '5 stars' portion, you can go a step further and assign a key-value property to an item, say 'STARS:' and a value, like '5'.
>search for the content by tag ("show me all books I tagged with 5 stars")
And this would be done by doing a search, a tag search, with this syntax specifically: `+books&+STARS="5"`
It's a very flexible system!