paint a matching color with the brick.

Fill the entire area of the middle peak with ship lap or other siding. Put a decorative vent near the top of the peak. Paint it white to match the garage door.

Or you could to the two peaks, or one like in in this picture. With a white banding board to separate the brick from the peaked area and then fill in the peak with siding and paint.

The banding board could go right across the tops of your windows. You can even do the little architectural detail in the peak like this picture.

The most likely reason that the triangle area of wall was not "bricked" when the home was original built is because that section of wall is above an open space and there probably is no structural support to carry the additional load of the brick.

I love painted brick - it looks clean and bright. You won't even notice the siding afterward. Makes your house look twice as big. Drive around any traditional brick ranch neighborhood. The best looking one are always painted. I bet the sell for more too. Paint it all a light grey or warm white. Add contrasting shutters and a bright colored door and you will some serious curb appeal!

oh and jazz up the light fixtures on the garage. A little money into some good looking lights will go a long way!

Have you checked to see if brick is behind the siding? If not I would just cover the remaining gable end with horizontal siding and do the same with the smaller gable end so they match.

Embrace the triangle by putting asymmetrical whit shutters on and doing some asymmetrical landscaping on the right side of the house away from the driveway. Then it will look more intentional.