Hello patm -
The image uploader is set up primarily to upload images from your computer to your Auctiva account, but you should be able to use the uploader for more than one image at a time to actually upload them to your account. It is not clear if you are referring to the upload process itself or adding images to the uploader in preparation to upload to Auctiva.
For example, if you have a series of images in a folder on your system and you open the folder, you can select multiple images by holding down the Shift key while using your mouse to select a range or the Ctrl key if you wish to select multiple images that are in various locations within the folder and then you can drag and drop to the uploader.
In order to look at your query more directly, please file a support case from under the Help tab of our site and describe the exact steps you are taking to upload the images as you have been doing and at which point you are running into difficulty with only one to upload at a time so we can have a look at your process and let you know what alternatives may be available.