So I was thinking about replacing it with something like NCM Random Image Pro 4.0.

You should be able to just use the vendors / banners module to do this, if you created a vendor for each section needed then also created a group name to match the vendor, maintaining information moving forward would be easy enough.

Updating ? you could copy all pics over as duplicates for one section to the vendor, then set the banner module on each sub page firing it up straight away and deleting the current module, then delete the pics from the old module, repeat until completed.