Yes you can! From the left toolbar, select clip art, then the category for the desired artwork. All available clip arts are displayed to the left and then can be dragged onto the calendar.
Adding Clip Art to Event Dates
Select desired clip art category.
Select the month with the event.
Click on desired clip art for it to appear on the calendar.
Resize clip art then drag it to the desired date.
NOTE: Although clip arts don't have an option to crop, they can be resized similarly to photos. Click to learn more about resizing photos.