Version: 4.1.1 (using KDE 4.3.2) Installed from: Ubuntu Packages In the "folder/browser view", a questionmark-icon indicates that there are untagged images in the respective folder. If one tags the missing images and goes back to the "folder view", the questionmark icon is still there, although all images in that folder are tagged by now. Only exiting and restarting KPA fixes this. To me it seems that the "untagged image" flag is not updated while working. Since this is an important feature when tidying up an image collection, I consider this as an irritating bug (I found myself searching for the untagged images (that were not there) for a long time).
I think you kind of misunderstood the userinterface :-) This is not a toggle with two states, it always looks like the check mark. In other words, there is not code in place to change the icon depending on whether you have untagged images or not. (Yes I know you have heard the following excuse before) Once I'm done with my exams I'll ask Nuno (of oxygen fame) to help me design the look of KPA, which for sure will include new icons.