Paul's Bods is one source of inspiration - he has some pics of a set of model pots and the like, as well as sacks of fruit and veg. They look great, and are just asking to be knocked over or thrown.
The other source are the comments on hugging walls, where Chris of Vaults of Nagoh mentioned improvisation and NetherWerks breakables and movables - both of them well worth reading.
Thinking of wargaming now then, what does a unit do when it runs out of ammo? Would desperate warriors pick up pomegranates if they had them to hand? Would they reach for and wield nearby earthenware, swing sacks or fend off attackers with handy urns?
Some general wargaming rule suggestions - they'll need adaptation to specific systems.
- Low ammo - A unit is out if a given proportion of rolls are minimums to hit.
- Impromptu weapons - Each terrain piece is assumed to be scattered with potentially useful items; in the open there is a 50% chance of availability.
- Fending off - A unit with access to impromptu weapons may use them, either at range or in melee; they are assumed to be of the minimum quality possible. A unit attacked in this way suffers a penalty to hit of one degree.