EDIT
Came across a problem with this and I'm reworking it.
.

This simple cart is made for 28mm scale fantasy games. It has room for 6 medium sized minis with bases. 2 miniatures in the front, and 4 in the back.

I didn't design the underside because I personally just plan to use the ones from here.

http://www.thingiverse.com/thing:582802

I recommend printing this on it's back, with the driver's bench at the very top. That said, I am still printing mine, so no clue if that will actually work at this time.