If you are having trouble getting your SVG logo to display correctly (or at all) on the Pixelgrade Listable theme, I have a possible solution for you.
On the forums a lot of people have been directed to this blog post here: http://creativedroplets.com/export-svg-for-the-web-with-illustrator-cc/
However that did not solve the problem for me. I realized that Pixelgrade is using, and that article is referring to, an older version of illustrator that has different export options for SVG files. On the current version of Illustrator there is an option to export the SVG logo as “Responsive” and this option is selected by default. If that option is selected then the logo will not show up on the site correctly. You must size your canvas to the exact dimensions that you want (preferably 60px tall since that is the default height of the logos div) and then export the SVG as a static non-responsive file. See screenshot below.
Hope that solves your problem. Cheers.