I keep getting this appearing in my logs... Aug 10 18:02:54 localhost gnome-shell[1699]: Could not load a pixbuf from icon theme. This may indicate that pixbuf loaders or the mime database could not be found. I looked around and saw that this problem had occurred in other instances, and to fix it, you'd have to reinstall the mime database or pixbuf. However, both of those reinstalls didn't fix the problem. I also observed that this issue gets triggered when I click the clock on the panel, and I have Spotify running. Perhaps it has something to do with the album image that is supposed to be displayed? Reproducible: Always
Created attachment 799225 [details] emerge --info gnome-shell
Created attachment 799227 [details] emerge --info app-misc/mime-types
Created attachment 799229 [details] emerge --info x11-libs/gdk-pixbuf
My guess is that you need gui-libs/gdk-pixbuf-loader-webp, but that's just a guess.
Are you still hitting this? I don't, at least in my setup with Gnome 45