Is there anyway to disable video/image posting for guests?
Admin control Panel > Users & Groups > User Groups > Guests > Forums and Posts Tab > Uncheck "Can post attachments?" if Checked.
I was referring to loading images video from outside sources such as youtube or image hosting. Instead I just want to show the link.
There aren't permissions that granular I'm afraid.
What about disabling sceditor completely for guests?
There's not a permission for the editor either, I don't think that's ever been required before. You'll need a plugin to achieve what you need here.