I want my users to be able to post images from other site (such as tinypic.com)  in a forum posts.. but I don't see any [IMG] tag in our beloved oxwall powered forum >.< so the only way to make it happen is to enable custom HTML for all user (Settings -> User Settings -> Content Input)

but is it safe? what kind of HTML that my users be able to use in there?

I wish they could only post img src and a href lines only..