I'm not sure what the image limit per product is, but I know that it's more than 3.
As far as getting listed on the search engines, Auctiva Commerce is optomized for search engines, and it automatically submits the products on your store to shopping marketplaces. It can take a while for search engines to actually pick up and add your products into their regular searches. I have my own online store, and it took about 6-8 months before Google picked up my items and started listing them. However, my store was not very search engine friendly at the time.