Thanks for the help on this. I have switched back to 2012 since for me Vectorworks is more for personal use than anything else. My settings on preview icons is selected and the 2012 files still show the preview. I do like some of the features 2013 has, but the lack of a preview is an issue since the majority of my files I make sure have a reference icon for my workflow.
As for 2013 workaround, I do a screen shot, then open in preview, select the area that makes sense to see, then go back to the file, get info and then paste the image onto the icon in the get info window. Long process but it works. Thank goodness I did not draw too many files in 13 as to make life a problem since 2012 can not open a 2013 file.