I presume you're referring to the process in the following screenshot:
This example (including URL formatting) is discussed in detail in the documentation page for the Callable Service template (especially Use Case 1).
The Control trigger makes sure that Create from Template will only execute if Boolean Branch exit's through the Yes trigger, which will in turn execute only when Is Image equals Yes. The name Control is solely a matter of convention we use, it is not a requirement (i.e any other name will function just as well).
As for the table name, it can also be anything you choose.
The red "X" signifies that the browser cannot display an image. This is probably caused by a some mistake in the URL (you can right click the X and check image properties to see whether the URL is as expected). I suggest you recheck the model, and especially the URL template used.
Note that there's also a slight chance that there's some browser configuration issue which prevent images from appearing (to dismiss this possibility run the original Examples application in your studio and verify that images appear).
For best results, use the Firefox browser..