The phrase "Pictures are worth a thousand words" is especially true in Role Play, for those that can't find the right word to describe something a picture does that for them. So pictures are very welcomed.
While pictures are welcomed they should be in the character profile. This is to keep things from getting confusing and unorganized. It doesn't mater where in the profile they are and how they're put up, as long as they are kept in the profile.
Finders Keepers...didn't think you'd hear that anymore did ya? I know we're all mature RPers here, but I'm making sure this is understood just to be fair. You can not use the same picture somebody else is using. It's just that simple, if someone else found a picture first, it's theirs to use. If they remove it and don't mind then it can be used, but if it's up, it's theirs.
Nothing offensive may be put up obviously. Of course different people have different tolerances, so if someone asks you to remove a picture because it's offensive - remove it. I don't care if it's a joke or not, remove it. In the case of character pictures, as long as nothing private is showing, it's acceptable.