So, while eating my lunch today I downloaded the DF trial to test out the command line utility.
Seems to work fine. I used an example that they show in their documentation for switching to a new desktop wallpaper. It takes a second or two for DisplayFusion to do this, but it works fine.
Here's the command I'm using. (The profile that I created in DF is called "Tropical Storm".)
<?xml version="1.0" encoding="utf-16"?>
<!--VoxCommando 2.1.2.1-->
<command id="306" name="display next image" enabled="true" alwaysOn="False" confirm="False" requiredConfidence="0" loop="False" loopDelay="0" loopMax="0" description="">
<action>
<cmdType>Launch.Hidden</cmdType>
<params>
<param>C:\Program Files (x86)\DisplayFusion\DisplayFusionCommand.exe</param>
<param> -wallpaperloadprofile "Tropical Storm" -wallpapernextimage</param>
</params>
<cmdRepeat>1</cmdRepeat>
</action>
<action>
<cmdType>TTS.Speak</cmdType>
<params>
<param>Please be patient. Display Fusion is randomly choosing a new image.</param>
</params>
<cmdRepeat>1</cmdRepeat>
</action>
<phrase>display next image</phrase>
</command>