This is not something you can do with placeables. Well not existing placeables anyway. What you are talking about is room model editing and/or creation. This has to be done in 3DS Max/GMax. It's not a topic that can be easily summarised in a couple of lines.
As for screenshots, you can enable them in the ini under the [Game Options] section, setting EnableScreenShot=1 and in K1 you can also use GUIsInScreenShot=0 to always take screenshots without the GUI just like in first person mode (doesn't work in TSL though). Using the PrintScreen button will save screenshots in the game folder as TGAs.