Image preview was supposed to be an enhancement but turned out to be an annoying feature due to slow performance. Responsible for image preview is the file \MMOS2\DLL\gbm.dll. The original gbm.dll was very slow. In the meantime there is a replacement in the package "Generalised Bitmap utilities" (see Hobbes) which is much faster. However, according to my opinion not fast enough yet. So, my recommendation is to rename gbm.dll in order to turn iconic preview off. Hope this helps.
Roland Reimers
Roland Reimers