Is it just me or is the mousewheel zoom backwards? Max zoom seems a bit weak too.
I notice you mention RAW support. Is that really your target market? It seems like people shooting RAW would probably be using a dedicated solution most of the time.... maybe not. As far as I'm aware there are multiple different raw formats from different manufactures and adding support for all of them would be a huge undertaking.
If I am to be honest, I don't like how the controls are. The text size could be 1-2 pts bigger. The whole popout thing seems pointless as the space isn't used when it isn't popped out. I think either fix it or make it user controlled and go all the way in with a tab.
The ?/? in zoom isn't very clear that that is editable. I think the ? should go in a text box.
I think it would be nice to see a custom scrollbar as well for the menu. It seems to distract from the look of the website which I like a lot.
Very cool overall. One thing you might consider for monetizing is https://www.theprintful.com/ or a similar website and let users get posters/prints and such directly from your site and all you have to worry about is integrating an API.