Working with CSS in Regions "Edit Region CSS"

I'd like to ensure that the repeating background image (gradient) is aligned to the bottom of the region. However, editing the css for ".upfront-region-container-bg" doesn't seem to do anything. My css code is as follows:

.upfront-region-container-bg {
background-position: bottom;

I select "tile vertically" but it always seems to default back to x and y tiling.