Hi Kbaker,
It doesn't seem like there's any way to add title or labels to the plot being generated from the Plot XY.vi. Therefore, I would recommend you to take a look at using a XY Graph for the purpose of creating a customized plot of your data. You have much more options for customizing a XY Graph than customizing the image from Plot XY.vi. In case you want to access the image of the XY Graph, you can easily do that by using the method called "Get Image".
Please see my attached CustomXYGraph.vi.
Have fun!
- Philip Courtois, Thinkbot Solutions