Fellow Newnanite here, there are more and more storage places opening. The one on Grieson Trail opened a new lot last summer, but not sure how crowded it is. I keep mine at Our Storage Depot on Hwy 16, it's grass and gravel, so not as nice as other places.
There is a new place being built right across the street from the place I use that looks like it will be super nice. Individual garages for boats and RVs. Looks like 14'x14' doors, and over 40' deep with power and lights. Only bad part is I heard they were $250 a month. It looks like they will have outdoor storage as well.