This is actually going to be an issue with your IIS/web.config and not with Kentico.
You need to tell the site what a .svg file is for it's content type. Specifically, you need to set .svg to be the mime type/content type of
In your Web.config, you'll need to find and add something like the below:
<mimeMap fileExtension=".svg" mimeType="image/svg+xml" />