Fixes:

Tracers - Accounted for the addition of the new 3rd parameter in builtin shell designs. Accounted for legacy tracers being loaded in the new builds. (Tracers should now not default to 0.1 length.)

Smoke generator - Steam effect now correctly uses drag, gravity etc.

Additions:

Decorations/Mimics - Added the ability to swap decorations to different materials, and added an emissive-only material. (These materials will have better names in a future release.)