This is just a little addon that extends the in-game design options for placeables. New configurations are added via the modDesc.xml file of any loaded mod.
Examples are in the sdk folder of this mod. More to come as more gets requested. Also, check out Trailer Park Farms 81 x 120 shop. It is set up to use these new features and is also just a great shop overall.
Finally, when creating new configurations, try to keep the same naming convention as other placeables. Configurations are currently game limited to 127 total. For example, if you want to make a roof color configuration and you know X other placeables already have one, use the same configuration name in your modDesc.xml. This will keep slot usage to a minimum and will avoid over running the limit. If needed, I will look into removing or at least upping the current limit.