I missed this thread yesterday, sorry.
There shouldn't be any reason not to see images in PM's except speed. Since images cannot be attached to a PM, they have to be linked to on another server. I know many people use photobucket or imageshack, these are great services but sometimes they're slow.
The fact the images isn't showing or that you have to refresh your page a few times might simply be because the images isn't completely transferred to your browser.
As for spoilers in PM's, I will look into it later today, I haven't seen anything about it in the admin panel but it could be hidden somewhere else. I'll let you know.