Hi there [EGC]Frugal,
You can go to your User CP and in the Edit Settings screen two options above where you can input your birthday, you will see a option for:
Mark Threads Read With Forum
(Marks all threads read when marking a forum read)
Check the box besides that option and then once you've read a thread and mark a forum read then you will not see New images besides any threads that have not had a new reply since you last visited the forum. If you do not have this setting enabled then all threads you haven't read will show as new until you do or temporarily when you use the Mark Forum Read button.
I bet if you and any member bothered by the New images like that can enable this setting and be a lot happier.
Have you enabled this setting sashagirl? If not I bet once you do it will be a lot nicer cruising forums.