I tried your code and it is working for me.
In MBProgressHud.h file, in comments it is mentioned that
/**
* The UIView (i.g., a UIIMageView) to be shown when the HUD is in MBProgressHUDModeCustomView.
* For best results use a 37 by 37 pixel view (so the bounds match the build in indicator bounds).
*/
So perhaps the image you used is missing or is noyt included. Please check that.