Residential Exterior Design

I think you have to go and learn 3d, what you did it 22 years old...However i like the border of the image you have done great inspiring design

I think put the landscaping and backround to make it more realistic why you dont use vray or other render engines for finishing

Looks like a standard Sketchup export. You know within sketchup there is a whole "Styles" menu that allows you to give each image a sketchy/watercolour/whatever look which will make your images far more interesting. Though if the sketchy look isn't what you're going for, there are dozens of free render engines out there that will produce photorealistic results if used properly. Check out Blender and Kerkythea. Some surrounding site & foliage would also help to put the building into context.