The artwork La Gerbe by Matisse was created in 1953. It consists of about 30 fern-like shapes on a white background. I am making a logo for a non-commercial academic website and it was suggested to me to use one of those shapes, albeit recoloured to match the website's theme. (There are intellectual reasons, and a kind of mathematical and visual pun why this particular image was suggested...)
I am aware that the EU copyright in this work expires in about five years, as Matisse died in 1954, and US copyright would extend five years beyond that.
I'm hesitant because while some fair use principles seem to apply (no effect on the Matisse estate's earning power; only ~3% of the artwork, and not representative of the whole; non-profit usage in an academic setting; original is a painting but new work is a logo for a wiki website), I don't quite feel 100% comfortable. On GraphicDesign.SE, where I first asked this, one user commented this was a clear case where it would be a copyright violation.
Any advice or resources that would help make a more solid case either way? (I respect the above-mentioned GD.SE user's experience and advice, but it is the say-so of one person on the internet) I've had a quick look around, but I cannot find any discussion about similar situations.