When I was MOTM I posted a couple news articles that month that had a good turnout. I can't say how much my karma increased but that's how the nominees are chosen. At the time I also posted in nearly every thread/made threads a lot so that contributed.
I got a line (I'm a skier) shirt, an "I'm a sexy skier" headband, a copy of less, some stickers and other stuff. Honestly, it was pretty rad. And shoutout to whoever chose the headband for me cause that was the bees knees hahaha