A transmission scheme based on rateless codes is proposed for image delivery over additive white Gaussian noise (AWGN) channels. Unequal Error Protection (UEP) characteristics are also introduced to provide prioritized delivery for different layers in content-based image. Firstly, layer segmentation processing based on an improved guided filtering is introduced to decompose the source image into the base layer and detail layer. Then, a windowing technique is applied to produce a bias towards certain classes of layers according to their various protection requirements. Variable-node degree distribution is also exploited to provide enhanced UEP and improve the high error floor suffered by some conventional UEP schemes. Compared with the conventional image transmission schemes based on rateless codes with UEP, the additional parameters introduced by the proposed scheme make it more general and flexible for individual applications. Furthermore, the proposed approach can provide better UEP performance and improve the network image transmission quality, which are confirmed both theoretically and experimentally.