You have some flexibility when designing your layout for mugs.

 You can use the "full wraparound" - like this:
 
  Another example here, showing how the main part of the image can be positioned on different sides of the mug:
 

Here, the entire photo will print:

Want the photo on the OUTSIDE of the mug, as you are holding it in your right hand?  No problem:
 
Other things you can do:

I just took a crop from an image, and put it on a canvas that was 1275 by 450 pixels, then added the text in photoshop.  The photo will wrap around the whole mug