This paper is concerned with the efficient transmission of scalable compressed images over lossy communication channels. Recent works have proposed several strategies for assigning optimal code-rates to elements in a scalable data stream, under the assumption that all elements are encoded onto a common group of network packets. When the size of the data to be encoded becomes large in comparison with the size of the network packets, such schemes require very long channel codes with high computational complexity. In networks with high loss, small packets are generally more desirable than long packets. This paper proposes a strategy for assigning optimal code-rates to elements of the scalable compressed data source, subject to constraints on the packet size, transmission length and code complexity. Our experimental results suggest that the proposed scheme can outperform previously proposed code-rate assignment policies, subject to the above-mentioned constraints, particularly with high l...