Plasmonic nanostructures promise sensing capabilities with the potential for ultrasensitive and robust assays in life sciences and biomedicine. Silver island films represent an interesting and straightforward alternative for the implementation of substrate-attached plasmonic nanostructures. The temperature-induced particle-forming behavior of thin silver seed films deposited on glass substrates and on polycrystalline silicon films is represented. The measured extinction spectra reflect the different size distributions and shapes. The covering of the particles with different optical transparent film materials like ZnO, Al2O3, SiNx, and SiOx leads to a further shift in the resonance maximum due to their refractive index. The SiOx system shows an additional long term change in the extinction spectrum in contrast to ZnO, Al2O3, and SiNx. Thin silver films covered with Al2O3 were used in order to proof the system as a sensor element for analyte detection (glucose solution).