Yes, but those old images still work with SSU enabled right?

What you have to do is: disable SSU, now add additional image, and see if they display.
http://public.rubikintegration.com/
If you want to make sure, upgrade to SSU 3.6.4 but I must say that this problem has never happened to us before.
The way IH2 works has nothing to do with SSU. SSU only interferes with link creating and interpreting, ih2 does nothing of that.