Mule train is finished!

The base is four 40x40mm square plastic Renedra bases glued together with sculpting putty to add extra strength. I also used the putty to affix the models to the bases. Here with sand/gravel and some grey stuff rocks:

Here primed with Vallejo Parched Grass primer and painted with a mix of Tamiya paints:

... and based using a range of products (Army Painter highland tufts, various Gamers Grass tufts, Woodland Scenics static grass and clump foliage):