Cooperative communications have received considerable attention for wireless multimedia applications as a means to improve reliability. To exploit such cooperation over slow fading channels, we propose to adaptively and efficiently transmit a layered source over a non-regenerative relay network. Specifically, we jointly determine the number of source encoder layers, the transmission rate and power for each layer to minimize the expected distortion of the reconstructed signal at the receiver. We show that having more relays can reduce the expected end-to-end distortion and that source adaptation with optimal resource allocation provides further improvements. Numerical results verify the effectiveness of our proposed algorithm, which enables low-complexity and adaptive streaming of scalable media source for future multimedia applications.