This right here -- I throw away that old "angels are pure and untainted, demons are the only ones give into lust". It's nice foundation, but judging by most of the responses, that's all people know about angels/demons and see.
I get creative with it. I want both.
I want angels that are assholes, that don't mind bending rules in their favor. Hell, if you think about the true lore, a lot of angels wouldn't have fluffy romances, if they'd want a romance at all. They'd look down on humans or at the very least would be too omnipotent to favor one human over the rest. So in my head, I'm like "my character has to be pretty damn special to get one of these falling for them".
And again -- I want my angels to be eldritch horrors. A lot of the protrayals in media seem to be based on Greek representations of angels. But if you go to other sources, like Ezekiel?
They look like elder gods.
That would be so much more cooler, and more romantic, to have a great being who is possibly beyond human comprehension fall in love with a human. That's cooler.
Same with demons. I want demons that are eldritch horrors but would set the world on fire for their lover. I've been picking that more for two of my stories: My Demon Valentine and With Butterflies in Her Hair (which is only on Webtoons now). They're demons that have drove many a men insane and ripped their souls away (that's more in WBIHH than in MDV), but they've melted under the love of a human.
I dunno -- I feel it you only stick to the traditional depiction in media, it gets kinda boring. So I say go past that and dive into the other lore. Maybe angels can be summoned in your world. Maybe they help with conditions that could take your sanity away. Maybe demons are only angels of a different mission.
There's a reason we have the TV Trope entries "Our Angels/Demons are Different". People dove into the lore, took some parts, and made something new.