League Merchandise (red response would be great)

So... I've got some great ideas for t-shirts and stuff (and the artistic and technical ability to make them a reality), and I saw this guy's post here.

I'm wondering what the policy is on League of Legends-themed merchandise. Are we allowed to sell things that are based on League of Legends or its characters? I'm sure it's a big no-no to include the League of Legends logo or the Riot logo, but I've got some really funny (imo) ideas based on some League of Legends themes and characters that I think would make great League of Legends merchandise. I've seen people selling various items in the past (a plushie teemo comes to mind), and I'm curious if we need Riot's permission to sell stuff like that.

Thanks for any input you can give!