it is beyond sggirls.com's knowledge and obligation to verify
the consent and approval of the subject in the uploaded
pictures.
as far as i know, trivia photograph has got no copyright unless you
specifically register it with the appropriate authority right from
the start.
posting it up on gallery like sggirls will not bring you any legal
trouble, provided that the picture is decent, not doctored, or
contain any form of defamation.
for detailed policies, please refer to http://www.sggirls.com/?action=photo_post_policy
in my personal opinion, if you publish your pictures freely on one
web site, it is not such a big deal for others to post it on
another unless it is commercially used, defamed or doctored.