A Google image search will find a picture of pretty much whatever you can think of.
To set up your avatar, click the Profile button up top and scroll all the way to the bottom. There is a box down there that will give you instructions on how to set it up.
I've never done a signature picture, but I'm pretty sure you just go to the window where you make your signature (under Profile, just above the avatar section) and place your jpg/gif there from a hosted source.
On that tip, if you want to post pics/screenshots/gifs-(like slicks)/etc. all you need to do is host it somewhere ( http://xs.to/ & http://www.imageshack.us/ are pretty popular ) and post the "direct link" link provided in the body of your message. Be sure to put
after it.
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