I kind of like the grey brick actually. I think you could add personality with more interesting garage doors. They are the prominent feature and what you notice most when looking at the house. Something with windows and/or more of a design would add a lot of personality.

To really give the exterior personality, I suggest stepping away from the grey brick for a second and look at the whole picture. What I see is a rather hidden entry flanked by two garage doors that dominate the facade. The first step that I would look at doing, would be to dress up the garage doors with a more interesting material.

Some examples of what I am describing are linked below:
http://www.zone4architects.com/projects/draw-drive/02.htm
http://www.zone4architects.com/projects/fuente.htm
http://www.zone4architects.com/projects/eastwood.htm

These finishes are typically applied to garage doors, which means that you could potentially clad what you have with a little adjustment to the door tracks to allow the thicker door to move past the wall.

As far as the entry is concerned, adding a gable over the porch would help to identify that there was something else to aim for between the garage doors.

I think once the big issues are addressed, the materials and colors will fall into place given whatever your aesthetic preferences are.

Hope that helps!