I have problems adding descriptions spanning multiple lines as the second argument to the \image command.
The documentation says that curly brackets are required if the description spans multiple lines, but that doesn't seem to be handled by QDoc.
What I get is the first line including the '{' as the alt text, and the second line including the ending '}' as the next line of the text.
Looking at the qdoc-files in qtbase, it seems like no-one are using descriptions longer than one line, though some use curly brackets.