The format of an email campaign can vary for a number of reasons:

1. Your colleague is using a different email client to you i.e. you may be using Outlook and they may be using iMail, Gmail etc. We have no control over the layout as it can vary from client to client. 

We do all our testing on the major business email clients i.e. Outlook, Gmail and iMail etc so the format should be pretty close.

2. Your colleague may have different default setting on their email client i.e. they may have block images as a default therefore when the test email comes through it shows text but no image. 

The only way to see images is to change the settings in their email client to enable images to be downloaded.