What are the specs for a background image?

I can’t seem to get a custom background picture uploaded with a high enough resolution without it crashing Prezi. What are the specs for a background image - ideally so I can zoom in on it?

Hi Sophie, 

Sorry for any inconvenience!
The  maximum size for any image is 2880 by 2880 pixels  (unless it’s inserted as a 3D background image). 
Here you can find more more information about it: http://bit.ly/1f1ySYJ

Hope it helps!
Best,
Nicole

Why are all the links for the help broken.  They give errors