I'm trying to stack 2 images on top of one another. In other words, 2 images centered top and two images centered bottom in a perfect grid. I need to switch images periodically otherwise I would just use one image and switch it as needed.

Any ideas?

use a table - 2 rows of 2 columns each

Using code right?

Build an HTML table in the post

I used wp table reloaded and it worked like a champ!

Thanks