I attempted to suggest this to jeb_ but I don't believe he saw my suggestion. I think buckets should be made place-able (just normal buckets and milk buckets) normal buckets could sit under dripping lava and water and on occasion or over time begin to fill up with the respective liquid. Although this would be mostly useless for water, it would make it possible to create lava so that you don't have to search for lava or try to get it in dangerous places. Place-able milk buckets could be used to feed cats for aesthetic purposes or if you wanted to breed cats. Please give me your feedback.
And perhaps a mechanic where if you're sprinting and hit a bucket, it knocks it over, causing it to spill the contents? Imagine, a placed lava bucket in a dark hallway...*evil grin*
If this is done, they'd definitely be square, so they might as well change the items to be the blocks too instead of an item.
I was thinking it'd work more like a flower pot on the ground.