It's not a bad start, but there are still things to do. I rather like the fact you gave plenty of headroom for the residents. You should probably consider the following in no particular order:
-You put frames around the windows which look nice. You should do the same with the front door.
-How many rooms do you want? What sort of layout? Open plan with American kitchen? Ask yourself these kind of questions before moving on to interior designing. If you want more rooms, consider adding another floor.
-Sloped roof would look nice. I'd probably use the 25 degrees ramps, as anything steeper might look too silly.
-Have you thought about a garage? If yes, you could attach it to your house. This would make the floor-plan less square.
-If there's enough room, you could try experimenting with adding another layer of walls as an "interior wall". You can have more varied rooms that way.
If there's anything else, just ask.