I read something recently which said that the modern image of angels as winged humans was actually not based on the original Jewish descriptions which were more abstract beings that have more in common with the bizarre creations of HP Lovecraft (8 winged polyhedron shapes for example). So, apparently you do not have to dig too deep into real world religion to find something unique and interesting...
If you have a link to that article, I'd love to read it. I've seen some art using more Lovecraftian concepts of angels, but I haven't been able to find the source for these versions.
Biblical angels are quite fascinating, and I like comparing the
various angelic hierarchies, but some of my favourite depictions of heavenly creatures come from the Book of Enoch (lots of angels getting up to non-angelic things like sleeping with humans, and a detailed ranking system for angels) and Dante's Divine Comedy does a nice job of making Heaven, Hell and Purgatory feel like real, vividly depicted places.
(Hopefully it's clear that I'm looking at these materials from the point of view of a fantasy writer who enjoys using religious mythologies as inspiration. I'm not judging them on their religious merits, which is a whole other kettle of fish.)