The traditional approach is to hand the designer a blank slide and say "we need a fresh PowerPoint template". You will get a slide back full of supporting graphics, logos, page numbers which shows that the designer added some value.
Here is the better approach: give an actual slide with content and ask her to improve that, including the template. The likely result is a well-designed slide. Now delete all the content and see what you are left with. It is likely to be an empty page... Here is your new PowerPoint template.
Oh, and the most important part of the template design project is not the template (i.e, the blank page). It is to make sure that the standard colors and fonts are programmed correctly. That's a programmer's job, not a designer's job.
In my presentation design app SlideMagic, things are easier. Upload your logo, use the color picker to select your accent color based on the logo, and you are all set.
Image by john.schultz on Flickr