Sure, Loki's gender is about as reliable as the weather. The character has been male, female, and horse. But so far Loki's appearances in the MCU (the most popular and widely recognized version of the character) have cast him as exclusively male. That's where fan creativity really shines.
"Kneel!" -subtext, probably Cosplayer elrincondeharlock did an amazing job with those scales and horns. Every tiny detail looks lovingly crafted. And that expression is 100% in-character.
This version, by Naraku captures the original playfulness of the character. I would definitely believe this version of Loki caused Ragnarok (and the destructon of Asguard, the Norse gods' kingdom) as a joke. I wonder what the horns are made of? They'd have to be lightweight, but sturdy enough to keep their shape.
SonicYvonne took this cosplay to the logical conclusion and did a fusion of fem!Loki and slave!Leia. I feel like Loki would approve of this outfit. The wig looks really intense!
Nicola Mariano knows that without Thor, Loki would be very bored. Both costumes are heavily adjusted from the MCU inspiration, and they look amazing.