Here's a link....
http://fivegallonideas.com/
They make plenty of accessories for 5 gallon buckets...
Camping storage and seat...
Always keep one in the boat as a bail bucket.
Make a huge water filter to clean rain water for pool, Koi pond, hot tub, and gray water uses! Gravel, sand, and carbon or charcoal!
Emergency food supply storage...start your kit today! Beans, rice, Oats, flour and food that keeps well in dry storage.
Use them for a bottom watering grow bucket system!
Upside down tomato planter!
Discourage lounging harbor seals .....
Build a party pontoon boat out of buckets....and other things...
https://robnoxious.wordpress.com/2008/08/14/shanty-boat-pontoons-made-of-trash/
Kiddie tree swing!
Bird house....
Shelving!
Just a few things I found while surfing...a also get free buckets from product we sell in smaller quantities.