The AT-AT's are Ertyl Models. Each model also comes with 2 snowspeeders and a Rebel Golan Turret. The Shield Generator in the lower right is custom made. The Snowspeeders have a hole drilled through them to slide up and down on the wire, mounted to a metal washer and nut. A small piece of foam below the speeder keeps it at the desired height.
The Rebel Hoth troopers are modified 6mm Epic Eldar, with their cone-shaped heads re-sculpted (a nip and tuck here and there) to resemble the Rebel Hoth 'Kepi'.
The Imperial Snowtroopers are also modified 6mm Epic Eldar. Again, with the heads re-shaped to resemble Imperial troops.
I needed a 'downed' rebel pilot or a few, so I converted some more epic.
In addition to the snowspeeder models that came with the walkers, I also have the Micromachine Snowspeeders which are identical in size.
For additional Rebel and Imperial troops, you can also find them in the Rebel Transport/Echo Base model from Ertyl. It also comes with a model of the Rebel Transport and a Millenium Falcon.