Simplicity can be beautiful all on it's own, and that house is quite charming, DeNile.
Personally, I would stick with the brick on the garage, but I'd change the wall covering on the living area to clapboard so it matches the upstairs. You could even use one of the siding styles with an edge-border where the brick meets the siding to add a bit of definition, although without doing it I'm not totally sure how it would look.
I think the landscaping looks really nice for a WIP, although it seems a little...puffy (I guess) by the tree outside the fence. I would suggest possibly getting rid of the big bushes behind it, and possibly going with some shorter ground cover type flowers. You could also use the move objects cheat to bunch the shorter flowers up to make it look like a bed, and accent the ground below it with one or more of the floral terrain paints to make it look fuller and add depth to it.
I would also suggest using the individual roof elevation adjuster to even out the roof on the second floor. All you need to do is click the button next to the "Remove All Roofs" button, and you can "drag" individual sections like you do wall decorations.
And if you were looking for a new color for the windows, it's hard to go wrong with white.