How to shuffle image files? Use Faststone Image Viewer. I have talked about this versatile program before. Here's how I did it.
1) Export jpg's of my images from LR4 to a folder on the desktop.
2) Right click on the folder and select "Browse with Faststone"
3) In Fastsone Image Viewer, select all images
5) Select all images. Select Tool-->Batch Rename All Images (F4)
6) Select Rename
7) Now the folder will have the shuffled images.