Sorry for the delayed response. We had some bug in our system and all the questions were hidden.
There isn't really a way to do using Zebra API. But, there are a few options though,
Some label design companies like NiceLabel have tools to do this.
Also, you can get an image from using the printer website by putting the printer on a network and using a browser to navigate to: for ex. http://ip_of_printer/index.html
You can go into the device files and enter ZPL to see a preview that can be copied as an image.
Hope it helps. Let me know if you have any questions.