Irradiation of solids with focused femtosecond XFEL pulses can drive them into warm dense matter (WDM) and populate excited electronic configurations that enable otherwise Pauli-blocked bound-bound transitions. These transient resonances substantially increase x-ray opacity and the elastic scattering factor. Here, we observe a transient enhancement of Cu elastic scattering near the L3 edge via Lα (2p–3d) transitions at 929.7 eV. The excitation sequence starts with photoionization, followed by Auger decay that produces high-energy electrons. These then trigger electron-impact ionization, creating a non-local thermodynamic (non-LTE) state. On a fs timescale, Cu ions remain at their cold-solid equilibrium positions while occupying excited electronic configurations with multiple 3d holes. Using XFEL pulses elastically scattered from a Cu-containing [SiC/Cu/B4C] multilayer, we spectrally resolve a multilayer-superlattice Bragg peak around the Lα resonance. Its amplitude and spectral width increase nonlinearly with excitation intensity. A self-consistent theory describing the formation of the non-LTE state and its x-ray optical properties links transient electronic configurations to the measured scattering response and reproduces the data. An effective two-level model quantifies a twelvefold enhancement of the imaginary scattering factor relative to cold Cu, demonstrating the role of transient resonances and enabling ionization- and state-selective contrast for ultrafast x-ray imaging.