Recommended Plug-Ins

ONE OF MY RECOMMENDED PLUG INS IS THE "REGENERATE THUMBNAILS" PLUG IN. IT IS MY UNDERSTANDING THIS REGENERATES ALL THUMBNAIL SIZES THAT HAVE BEEN "PREVIOUSLY UPLOADED" TO MY MEDIA LIBRARY. I HAVE NOT UPLOADED ANY IMAGES TO MY WEBSITES MEDIA LIBRARY THAT I WILL NEED WITH PERSONAL TRAINER PRO. SO I REALLY DON'T NEED THIS PLUG IN. IS THAT CORRECT? I WAITED UNTIL I CHANGED MY THEME TO PERSONAL TRAINER PRO BEFORE I STARTED BUILDING MY WEBSITE AND MEDIA LIBRARY. THANKS.