well there is tons of stuff out there doing this job pretty well already. my new favorite one for this job is milanote which i am currently testing. awesome concept. you should also have a look at raindrop & dropmark.

i was a big fan of iceber.gs until it shut down. and tbh i find myself using pinterest for moodboards more and more often.

I wrote a tiny JS library for making mood boards quickly. Unsurprisingly, it’s called Moodboard. https://ntlk.github.io/moodboard/

It meets my requirements — no UI and no intermediary service that I either have to pay for or see ads on.

We use InVision boards. We generally share most projects & prototypes over InVision, so it's nice to keep mood boards in the same family.

We are building Collectie app for creating moodboards. You can add images, notes and bookmarks. New version with a new UI and new features will be available soon

Niice is my recommendation. It's pretty close to perfection.https://niice.co

Thanks everyone for your comments and suggestions. Got to say Milanote looks amazing.

I really like using pinterest as a mood board tool, but also don't like it because it's pinterest.