Hi Himilce;
I saw your post and lamented the fact you painted the front door black. When I see a recessed door like that, I would try and paint it a light, bright, color, to accentuate the entrance and make it more welcoming. Now that it's done, there's no sense going back and repainting - instead, I would leave that front door light on to brighten the entrance, at night, during the day, anytime the house is being shown.
Another thing I would consider, this house, like many newer homes, screams WELCOME TO MY GARAGE DOOR! Anything you can do to de-accentuate that giant wall of white will be good. If the budget allows, you could swap out the top panel of that overhead garage door, with a panel with windows. Alternately, you could use black paint to paint faux windows there. Also, for less than $40, you could buy faux decorative black hinges and handles to add some interest to the garage door.
Then, like others have mentioned, a white window box filled with colorfull flowers, a pair of shepherd hooks with two matching flower baskets, and some dark mulch, would add punch.
I used photoshop to create a picture of what I'm describing.
Best of luck with your flip!
Jerry