I have a parametric bed frame procedure already! It's demoed in an example project here https://sawdust.diy/share/60d515eb-ca3f-559e-994f-56164dd1fc... click 'open the workshop view' to see the full UI, make a new one using the bed frame procedure in the procedure tab (or add MCP and ask the agent to use the procedure).

And you can customize it beyond the existing design by asking an agent to modify it, e.g. "let's use walnut 4x4s and 2x4 slats", "I don't like how the corners come together, can we make it more like traditional joinery?" Also, staining is a supported procedure (it's very useful for e.g. coloring geodesic dome struts by strut type), you can just ask the agent to stain the pieces with whichever color you like, I'm sure you could even use a named stain you want to use like "Minwax Dark Oak" and get something pretty close.