In the field of materials research, a novel alloying concept, so-called high-entropy metal-sublattice ceramics have gained a lot of interest in the last years. These consist of a solid solution of 5 or more binary ceramics leading to a high-entropy metal-sublattice. Within this work, we investigate the structure, mechanical properties, and thermal stability of thin films based on (Al,Ta,Ti,V,Zr) with different Al contents. For coating synthesis, we used a single powder-metallurgically produced composite target and additional Al cubes placed along the racetrack to increase the Al content within the coatings. The coatings in as-deposited state show a fine-columnar growth and crystallise in a single-phase face-centred cubic (fcc) structure. The hardness of our coatings in as-deposited state is ~32.8 GPa and relatively independent on the Al-content. We studied the influence of the Al content on the thermal stability by investigating the structural evolution of our XRD, as well as nanoindentation. The study reveals a distinct influence of the Al-content on the decomposition of the solid solution into an fcc-matrix and Al-rich domains.