I noticed .jpe (image/jpeg) is not part of the Attachment Types allowed by default, you can add it, but really it should be there. I know its not very common, but I have run across .jpe files basically .jpeg files renamed for DOS
I used to have a mod in MyBB 1.4 that would default to a certain post icon if the No Icon option was chose, but this solution no longer works in 1.6 Beta 2. http://community.mybb.com/thread-35864.html
Any ideas on the changes needed to get it to work?