The issue reported by peter is related with https://moodle.org/mod/forum/discuss.php?d=65819#p903924, too.
Now, we have tried to change main Moodle site from Moodle1.9 to Moodle2.4. I had upgraded old course data and restore it to new clean moodle2.4 site, however Wiki contents containing images aren't displayed since attachments does not restore for filestorage.
The cause of the problem is just same as MDL-35305.
I debuged and found out a solution, then reported it yesterday.
The MDL-35305 is assigned no assignee since the issue was reported as minor priority. I think the bug is very very very important and critical, so not minor!
Please vote to the issue for assigning a assignee from moodle HQ!