You can insert a picture, if you've previously uploaded it somewhere. Then again, a link is fine.
What is your startup setting?
It is just a file on your computer, Opera converted your old Notes to HTML so the new version could read them. You must have clicked on the "Opera 12 Notes.html" desktop icon. Close the tab (so that if you are using "Continue from last time" it won't re-open the file), and then don't click that icon - look for the real Opera shortcut.