Yeah, lets see how hard this is to fix..
Imagine this.. under the menu's in konqueror... they have a submenu labled.. of all the terrible and worthless things to name a submenu...
Now I wonder why they would put a thing like that there.. and gee... what are all these other options for.. the ones called "Images, Cursors, Sound files"... And they all have these little check boxes next to them.. hmm...
The reason for the sarcasm? Well, perhaps because actually looking through the menu's in konqueror, the heart of KDE, before posting a question asking how to turn off a preview, would have been a reasonable effort on your part.