Hi grannie on ebay,
Fortunately, you should actually still be able to highlight multiple consecutive images so they can then be selected through the new version of the uploader, but the exact process you need to use is a bit different than the previous one.
In order to select a series of images, you will first need to highlight the first image by clicking the area surrounding the image (not the checkbox) and it will become highlighted. Then, you can highlight the rest by holding the CTRL and SHIFT keys and selecting the last image in the series in the same manner.
Once the series of images has been highlighted, you should be able to select all of them by clicking the box displayed to the upper left of any of highlighted images.