I think part of it is just knowing there's gonna be something freaky in the thread, so chances are you'll scroll down slowly and get accustomed to whatever it is. It's best to show something freaky on the first post of a new page, or an animated GIF that changes to something freaky, or best of all, link to an image (preferably small so it pops up at once instead of slowly revealing itself. I think you turn off Progressive under JPEG settings for that to happen).
So your image would have been freakier if you had linked to it instead.
Like so.
After all, a link to an image is part of what made me lose to smiledog so long ago. Because you have no idea going in what you're going to see.