Can silver metal be used to electrochemically reduce copper?
In principle, electrically depositing copper(II) ions onto a silver electrode should be possible. As it should also be possible to deposit those ions on just about every other cathode in existence as long as there are no more noble cations in solution.

However, depending on what you want to do with the copper, you may run into problems. Do you want copper-plated silver? That should be fine. Do you want to redissolve the copper to get a pure solution by acidifying? In that case, you cannot use the typical $\ce{HNO3}$ method because that would oxidise the silver, too, and you would end up with a mixture of copper(II) and silver(I) nitrates in solution.