I stopped at Wal-Mart today and in the clearance aisle, they had some sets called Nature's Wonders:HD. There were two different sets, both on clearance at $7, down from $15. The set I picked up is a safari set, with a rock ledge, acacia tree, oasis, and two boulders. The other set was a farm set, with some fence sections, two bales of hay, and a windmill.
The packaging is a completely enclosed box, so I couldn't see the size beforehand, so I didn't buy the farm set in case they were too small. After opening the safari set, I think the farm set may be in-scale, or if not, just a smidge small. I'll try to get pics later, and there's no website to point you to, as you have to have a registration code (found in the box) to get in. Anyway, the safari set gives some good accessories.

Just took some pics with a Cobra trooper, I'll try to post them up in a bit. The rocks and oasis are fine with Joes, but the tree is just a bit small, but would work.
I found the code to get into their site in the bottom of the box. It's weird they require a code to get in the site, since they offer pictures of their items, plus stuff for sale. Haven't tested to code to see if it is multi-use, but if anyone is interested, it's n92-030a