The popularity of online free album services in the recent prevailing Web2.0 paradigm has posed great challenges to the existing image storage systems. In this paper, we analyze the characteristics of online image storage techniques from a system perspective. We present a novel framework called OBSI, which stands for an object based storage system for storing and retrieving images of online album services. In the design of OBSI, we employ a novel divide and conquer approach which subdivides OBSI into two layers: an object layer and a chunk layer. The chunk layer handles the "dirty work", such as disk space management and reliability guarantee. The object layer provides a uniform object storage and retrieval interface to applications. OBSI reduces disk access by employing a simple and yet effective storage allocation algorithm which allocates storage objects continuously as clustered to their respective metadata. Experimental results show that OBSI provides high efficiency and throughput in image storage and retrieval services.