Well, in my group we are planning our gaming table these days, and we have the garden of Morr on the shopping list
along with some not dead trees, hedges and bushes. The way i see it vegetation is a great way to show the decay of a ruined city.
Mordheim is huge and the part you build could be outskirts, and quite far from the Pit
also i would say it depends on the chosen time setting. We want to create a table representing the city just after the meteor strike.
If you want it to look like the city was destroyed a while ago, id say visible corruption where the way to go
Also, if you dont want vegetation on your board, apart from the deco in the graveyard is say the mystic feel tells its own story. "Aye... These are the only things that will grow in this damned place"