I would love to have that room!
I googled "storage in a room with a sloped ceiling" and there were several links with good ideas. Do you have an Ikea nearby? One or two specifically use their products, although I'm sure there are things that are not from Ikea that would be similar.
Hopefully, if you click on this link, you'll see the highlights for the search I did. Maybe something will appeal to you.
https://www.bing.com/search?q=storag...3a943295d60941