Most users just turn the screen saver off as it slows down the crunching of the models by diverting computer resources.

---

It's unselected in the extra page linked from the 3rd screen of the install procedure for BOINC.

But it's just a screen saver, and so will appear in the drop down list of screen savers accessible by: right-clicking on the Desktop, clicking Properties, and then Screen Saver at the top of the little pop up window.

I use Blank as a "screen saver", and, as Jim said, most seasoned crunchers won't be using the built-in BOINC screen saver, so you'll probably have a hard time getting an answer to your original question.

If you want to see the pictures now and then, there's a button in the Tasks tab of the BOINC manager, labelled: Show graphics.