Just some ideas
If you have the designer or the digital photo or the address you can look up better pictures to work as an inspiration, maybe if you a re lucky some plans from arch daily or dezeen, etc...
1. use the 2 1/2 grass instances and the fur plug in http://www.suplugins.com/help/grass-tutorial.php
2. use another texture for the sidewalk (looks "plastic") there's some excellent urban system on the browser with sidewalks and materials, details on the joints for each slab, etc. volume and round corners plug in
3. it will hit the render time, but try populating the the left side with 3d stones (make them simple low polys) make some tests with only that to see if it helps the overall outcome
4.all the wood texture looks unnatural maybe try to use another type of wood with more life, grain etc. also round the corners of each element (that helps with the shadows and overall feeling) also use the eneroth's randomizer for the canopy over the window
5.extrude the entrance slab stones if they are meshes use the plugin Fredo6: Joint Push Pull Interactive ( they look really flat maybe try another texture, me aware of the difference between projected textures and normal textures on sketchup
6.the browser has the right texture for that type of concrete just need to scale it down a little bit
7. add some turned off lights on the ceiling of the garage
(round corners on everything, make a backup before making that)
make lots of tests and have patience, you can do it!