What would a diagram of the metal lattice structure of CuSO4 look like?
From the WebElements.com page on copper sulphate, the metal lattice structure looks like:



The yellow pyramids are cooper and the other structures are sulphates.

An alternate view comes from the Wikipedia page of copper (II) sulphate:



The pink spheres represent copper, yellow are sulphur and red are oxygen.

Below is a 2D representation of copper sulphate, from the Royal Society of Chemistry



A similar question with some more insight is found in How do copper sulphate and the like change crystal structure on adding water of hydration?