Ok I found a work around that WORKED!!!!
First I am running iTunes 12.1.0.50 on an external drive connected via my Airport to my computer on Mavericks 12.9.5
This is what I did:
1. Add an extra "dummy" movie
2. Select the movie I want and the "dummy" movie, then "Get Info" (click "Ok" if you have the editing multiple items warning pop up)
3. Select Artwork tab, the click button "Add Artwork", Navigate to file location desired artwork, and click ok
4. Click "OK" on "Get Info" box and Wait.
5. Wait, and Wait some more. took like 10+ min to process (the whole time iTunes had the spinning circle)
6. THE ARTWORK FINALLY APPEARS!!!
Note: First attempt the art work was on the computer hard drive while the iTunes library is on an external. Took 10-15 min to process.
Second attempt, I created a folder (outside of the iTunes folder) on external and placed needed artwork files there
Then did steps 1-6, navigating to the artwork file on the same external drive as my library,
The finally process was MUCH Faster, like took 5 min instead of 10-15min.
Both Methods were successful.
I hope this helps everyone out till apple fixes this issue.