The smell of melting foam isn't the best for sensitive noses but we used to use polystyrene ages ago which released cyanide gas when melted/burnt!!!! Although legend has it that cyanide "smells" like almonds you will forgive me if I never try to sample THAT one!!!!
When we had large areas of broad light that needed to be broken up I usually headed down to the local camping/army surplus shop near whatever studio we were shooting and buy a cheap "off-the-rack" camouflage net and stretch it on whatever frame would suit it's size and use that to get a more natural looking shadow too. Keeping in mind that a kookie look, if it remained sharp, would start to look obvious ...... as you move whatever light modifier towards the source and away from the set, the softer the shadow will look; subtlety being the operative word here although things like signs painted on windows, venetian blinds, window frames, "bad man" standing in the corner, creepy door opening slowly etc. etc. always look good with a hard shadow. Sometimes the shadows can tell the story – Hopper (the painter), Martin Lewis (etchings); also look up "chiaroscuro" in Wikipedia and check out the "Photography/Cinematography" section.
One last thought is what we use on stage – the profile spot. One can add gobo's to them to create patterns of light and shade on a surface ... the lamps can also be de-focussed to take the edge off them (http://www.rosco.com/gobos/). Cheers! Sam