Most image library systems develop Web sites to speed up searching, downloading and buying processes for customers. Except the e-commerce capabilities (such as the instant access, the e-payment, the online download, the convenience, the content variety, etc), a web-based image library should offer more attractive services to gain popularity. In this paper, we propose an online installment payment scheme (OIPS) based on the image secret sharing approach. The proposed OIPS gives customers a novel and useful payment plan that if one cannot pay in full to purchase the high-resolution images one may pony up a buck for each low-resolution image from the Web site to preview. After making a full payment, a customer can reconstruct all high-resolution images accompanied with a certificate for protecting the copyright of owner's rights.