Here are 2 vehicles I scratch built for my Eberron campaign.
ELEMENTAL LAND CART
This is essentially a wagon with a bound earth elemental. In hind sight, I wish I had built a more traditional wagon out of balsa wood, and then wrapped it in stone. However, this certainly is a serviceable piece. The cargo bed can fit 8 medium sized humanoids (ie 20mm square bases), plus a driver on the bench.
ELEMENTAL POWERED SKIFF
In Eberron, in addition to sailing ships, they have airships. The airships fly under the power of a bound fire (or air) elemental.
My players managed to acquire their own airship. (I will post a map in the near future) They would often leave the it a short distance from their destination, taking the skiff the last bit. Having a model of the skiff was going to be convenient.
This skiff (or raft) is a WIP, belonging to a much larger vessel. This model can fit ten 20mm bases on the deck.
We ended the campaign soon after the players took control of the airship, so this piece never got finished. It was only used for 1 or 2 sessions. The players occasionally show interest in returning to the campaign. One idea is to have the characters retire from adventuring and "set sail" on a new chapter. The characters were around 12th level and it would be nice to take them up to around 15th level.