Creating A Loading Circle

My website is [login to view URL] (an online whiteboard). Currently, if you go to load an image the screen will fade out and it will say "Loading Image..." What I want is an animated loading bar similar to that of Youtube before a video loads (the loading circle). I would like the animation to be GIF. Also, the background of the image must be translucent/clear (not white). If you have any questions let me know... Thanks, Jordan