Image Module Layout Customization

Hello,

I am using the "right side bar" UI layout, and the only module I have in the side bar is "Images."  When I have more than one image category available, those categories display side-by-side in groups of two before stacking.  

I would like the categories to display one on top of the other ... one at a time.  In other words, I'd like the categories to be stacked vertically, rather than display in groups of two stacked on top of each other.  Just single image categories stacked vertically in the side bar.

Is this possible?

Thank you in advance!

-Mike