Hi!
I just checked a few of your uploaded images in your account, and it appears that they are quite small in size. I don't know if your camera setting is making them so small, or if you are resizing them down in Picasa before uploading them into your Auctiva account. Our uploader will automatically resize some images during the upload process if they are too large, but not that much. If you can take larger images, then they will be larger in your listings.
Some of the photos I looked at in your account were for a dress and many were around 25-30KB and 350px x400px, which is very small. And when they are that small, of course they cannot be "supersized" very much when people click on them in your listing on eBay (mine average around 100-150KB and 800px x 1024px.)
See if you can make some adjustments and have your images saved at a larger size before uploading. That should solve your problem with the images being too small once uploaded.
If you still need help, feel free to contact our Customer Support. Good luck!