This requires a bit of work from you as a toolbar administrator but the results will be worth it. If you are looking to load icons to your toolbars which your users will still be able to manipulate, the steps below will give you the result you are looking for. 

Firstly, your vector graphics should be saved as .EPS file or .PDF files (If you are using EPS, please convert to PDF before continuing).

Next, you need a tool that is able to convert from PDF into a file format which PPT will be able to open, whilst still maintaining its vector qualities. EMF is such a file format (Windows vector graphics format).

 In the example below we use a free tool called Inkscape.