2D Drawing architecture

I want to create something like a game but I am going to use Direct2D and GDI for drawing API.My problem is that I want to separate drawing code from objects. For example lets say I have conduit objects and pumps.Each one might have different color and vector shape. I mean problem here is that drawing a pipe wont be a texure but a series of commands like drawline , drawrectangle etc.The only way I can think of having a Renderer class that would have drawing logic for each one.But in case I want it to be extendable from another developer then in order to add a new object they should extend renderer. My question is since I am not going to use classic game things like sprites,textures etc how can drawing complex vector objects be abstracted? And how can I make it extendable ?