I didn't test it, so I actually don't know where it's placed :smile: It was mostly to be able to get rid of duplicate images in core and calendar and be sure to use the right one in case core changes it.
I guess you could do something like:
`<div id="fullcalendar"><span id="loading" class="loading" />` Not sure if it should be span or div, and you would probably need to set height/width on it.