Warning for KroozeArcade plugin - it's not good idea, because then you need to change path to play.php (or I don't know how to change path after finishing game). And because original solution suppose new window, there is buttom close window, so it needs to be changed to go back button. So there is more work than just use lightbox library.
i found use the light box gallery (prettyPhoto) its installed on the plugin manager, where is the codes for it to work with the light box i am using on this page? you will notice the light box is white. but the one in plugin manager is black. http://www.outlawsgameroom.com/page/videos
You should be able to add attachment? Just don't use quick answer and use that with editor. If it's core setting - that dark square, then create issue on core github here: https://github.com/e107inc/e107/issues In Chrome you can insert image directly by ctrl-v there.