The work on the bases is good and well worth the effort, it sets the models apart. The metal looks quite flat and non-metalic on your models. A bit more shading or even adding some "chips" to the edge to simulate battle damage could really improve this in my opinion. Some of the models also seem to lack contrast and the parts seem to merge, try adding a few more neutral, organic tones to break this up. They are very cleanly painted though.