EDIT:The problematic issue seems to be exclusively in Dolphin. I do not, for example, find it a problem with gthumb
When loading a folder that has a large number of images, the presentation of the thumbnails always takes a long time, and until they are all loaded the sequence of the images constantly changes; making selection almost impossible.
I suspect the problem is that thumbnails are always retrieved in a "sort by name" sequence. But if the folder is sorted "by date, descending" the mismatch between the two creates a rather long wait state for the user before they can click an image.
This is particularly annoying in situations where the user is opening a web browser "file upload" dialog to upload a single image file.