The most common conventions are based upon industry, profession, and fandom.

Ready for Desucon 4 ! Picture taken by Sven.

Rina ♥

Sven and Rina.

Cosplayers.

Desucon 4, a sci-fi-fantasy-Japanese mayhem of an convention, at Oslo Kongressenter. And as always it was a messy blend of cosplayers, weirdos, Poky and noisy fan-boys and girls.
We had a blast.

I don't know if I've mentioned this, but I'm huuuge Star Wars fan. And there were storm troopers present, guess who spent hours just chasing them around ♥

Yay! A storm trooper!

A jedi and some storm troopers.

Boba Fett ♥

V and Rorschach. This picture is awesome...
Oh, and it actually my good friends Martin and Christoffer.
Rorschach.

Naruto cosplayer.

A Charmander and a Pickachu.

Idril's skirt.Thea and Stian. We all had a bit of a Desucon overload.