To make it work you need two things - to add Logo URLs to the sponsor settings page, and to install the Sponsors Block Plugin.
See this patch to allow you to add URLs for logos to your conference sponsor settings page. Here is what the results might look like for you. If a logo URL setting is defined, it will draw the logo, otherwise it will display the institution name and URL to their site.
Download the plugin package below image to enable the block in your block listing.
