Can't say as I've played with it much but, may the following will work;
- Attach all pictures
- Add all text
- Highlight all pictures and text and click the insert spoiler button
If that doesn't get what you want, go to BBCode Edit mode and see what you can get to work there.
Do not jump back and forth between BBCode and Rich text edit modes. Once into BBCode edit mode, stay there until you're finished. Weird things happen when switching between modes.
Something like this maybe?
I suspect the attachments don't show up as full pictures in my post because they aren't pics I've uploaded. I did the spoiler stuff, copied from BBCode edit mode from your previously quoted post, edited it how I wanted then cut/pasted it in to my post here in BBCode edit mode.