Well, pretty much anything you want! There are a few things you aren't allowed: * Personal images. Per the images and media policy, All images hosted on the wiki must be used in the main article namespace at least once. You cannot upload an image solely for use on your userpage. * You also shouldn't upload an image, add it to one article and your userpage, unless it complies with all the points of the policy and is superior to any existing image of the subject. * You're allowed to use images already on the wiki on your userpage as much as you want. * Personal images of your character can be hosted externally, but more on that later. * Flaming and personal attacks. Your userpage shouldn't be used to flame or personally attack any user, per the user treatment policy. Cons