sudo apt-get install gnome-raw-thumbnailer ufraw-batch
Check to see if everything works, and your thumbnails show up. If not, try the next part.
In case the default config does not work for you, try this:
Edit the file /usr/share/thumbnailers/raw.thumbnailer as root and insert the following content:
[Thumbnailer Entry]
TryExec=ufraw-batch
Exec=ufraw-batch --silent --size %s --out-type=png --noexif --output=%o --overwrite --embedded-image %i
MimeType=image/x-3fr;image/x-adobe-dng;image/x-arw;image/x-bay;image/x-canon-cr2;image/x-canon-crw;image/x-cap;image/x-cr2;image/x-crw;image/x-dcr;image/x-dcraw;image/x-dcs;image/x-dng;image/x-drf;image/x-eip;image/x-erf;image/x-fff;image/x-fuji-raf;image/x-iiq;image/x-k25;image/x-kdc;image/x-mef;image/x-minolta-mrw;image/x-mos;image/x-mrw;image/x-nef;image/x-nikon-nef;image/x-nrw;image/x-olympus-orf;image/x-orf;image/x-panasonic-raw;image/x-panasonic-raw2;image/x-pef;image/x-pentax-pef;image/x-ptx;image/x-pxn;image/x-r3d;image/x-raf;image/x-raw;image/x-rw2;image/x-rwl;image/x-rwz;image/x-samsung-srw;image/x-sigma-x3f;image/x-sony-arw;image/x-sony-sr2;image/x-sony-srf;image/x-sr2;image/x-srf;image/x-x3f;
Check if the mime type of your RAW images in in the MimeType list.
After that, stop nautlius and clear the thumbnail caches:
nautlius -q
rm -rf .cache/thumbnails/* .thumbnails/*
@smac89, "nautilus" is spelled incorrectly. Thank you for the notes. Unfortunately, I am still not having the thumbnails generate properly.