Mock-ups
What are mock-ups, defintion and links: Mock-ups are 'very early prototypes' made of cardboard or otherwise low-fidelity materials. The user, aided by the designer, may test the mock-up (imagining that it works) and thus provide valuable feedback about functionality/usability/understanding of the basic design idea/etc.
http://www.interaction-design.org/encyclopedia/mock-ups.html
General examples: http://mockupstogo.net/
1. You need to have a screen shots of the existing site and point into the images where do the usability problems occur (see example below; figure 1). You refer to your usability report to base and justify the problems.
2. After the presenting the existing site usability problems, you display the improvements and describe how they solve the problems mentioned (see figure 2).
Usability problems found in the usability tests executed alst spring about the use of KPE and is information presentation.
Figure1. Presenting the problems of KPE info tab. Click the image to see it as full size.
I cannot refer here to the usability studies because there were so many and they are not with me at the moment. However, here you can refer and copy the what the users said in the test, e.g."It is annoyign to click all the little arrows to see what is in the end of the infotab". "Why I cannot edit from here the description of the item, I have a spelling mistake there" , etc. Or you can refer to your notes from the observation, i.e., when you saw that the user had a problems you can write that here, or in your refer to the issues that came up in the interviews and questionnaires.
Below is the mock-up of how to improve the above Info Tab. 
Figure 2. Info tab when items have not been selected (notise that thee is a lot less arrows and all information that is related to each other is close by). 
Figure 3. Info tab when a tailored view item has been selected (notice that you can select from yp and down other information, still every on is still n view)
Figure 4. Tailored View info tab in edit mode (notise how the editing can be executed directly from the inof tab, no unncessary clicking to other places to edit whatever the user needs to edit from the information of the selected item)