If you would like to add a gradient to the Background of the Stacks Menu area the open up your Terminal.app and paste the following text and press return.

defaults write com.apple.dock mouse-over-hilte-stack -boolean YES
killall Dock

Your Stacks will now look like this…

After clicking on a stack so that it fans or grids out, hold the Option key down, and then click on as many items as you desire within the stack. As you click each, it will open and the stack will remain onscreen. Unfortunately (at least when selecting folders), items will open behind what ever program you happen to be working in at the time.

Stacks