to what Hans said.
model maniac, take a few minutes to fill out your profile too; it helps us know a little something about you--if you're just a kid starting up, or a new modeler, or whatever?
This is raw, first-stage diorama building, and it's a good start, but now you have to go beyond the rudimentary placing-of-figures and set pieces in order to really draw the viewer in and impress them with the realism of your work. You must consider beyond what are just the elements--the soldiers, the armaments, the sandbags--and think carefully how each one of these individual pieces--even each piece of each piece--might show wear, weathering, some individual trait or quirk that gives it realism and life?
The groundwork, as Hans mentioned, is one of the most important elements in diorama building. It is not sufficient to put down a simple grass mat, unless you are modeling the well-manicured lawn of a governmental building or golf club house--and then again, if you are, you must make the viewer aware of that, and tell them why in some way. Go out and look at real ground--look att he veriety of plants, of bare patches, of the diversity of cover--there is much to be learned.
Try to get a hold of the great Shep Paine book "How to Build Dioramas"--here is a link to it on Amazon.com:
http://www.amazon.com/How-Build-Dioramas-Sheperd-Paine/dp/0890241953/ref=sr_1_1/102-9370310-9224930?ie=UTF8&s=books&qid=1185569293&sr=1-1
It will tell you everything you need to know!