Svg files are actually XML files, and by default will be processed and displayed as XML files. The internal browser view of Ultra Recall uses Internet Explorer technology to display content, but Internet Explorer also treats .svg files as xml. You need to install a plug-in/viewer to properly interpret/display these graphical .svg files (either in your browser or a stand-alone application).
Do you have a viewer installed for svg files? One example is the Adobe viewer:
http://www.adobe.com/svg/. Other viewers are available, but this one is free, and registers a plug-in to Internet Explorer which allows Ultra Recall to display .svg files internally.
My testing indicates that with this viewer installed, you don't even need to add .svg to the list in Ultra Recall, they properly display in the internal browser view (based on the underlying .xml filetype). One issue I did notice is an omission of scroll bars (in the Item Details Pane) which seems to be due to this particular viewer (I see the same behavior in Internet Explorer).