I usually use one of my API Baby Grands when I'm
going to be on stand all day. They have a comfortable
seat and a large platform. No backrest, but you
can pick up a camoed pad that will strap around
the tree for less than $20. I picked one up at
Cabela's or BPS a couple years ago, does a good
job.

Here's another back pad/support I came across
the other day. Looks like it would do a good
job when used with a treestand.
http://www.turkeyhuntingsecrets.com/...odbackmate.htm

TB