An argument that visual memory can, in principle, be improved

My last two posts were "From 'I cannot mentally visualise' to 'god what a taste of fire'" and "'Attention restores forgotten items to visual short-term memory'". To me, the second answers a question that the first poses. Namely, is it possible in principle to improve visual memory?

The research by Stokes and colleagues described in the second article shows that visual memory is affected by attention, and that memory for specific items can be improved thereby. But we can consciously manipulate our attention. Therefore, we can in principle improve visual memory even though we may not be able to consciously change its storage capacity. Of course, the improvement might not be large enough to be useful. I'd welcome comments from experts.