Hi konorg,
I have found 2 ways to simulate this:
1. Physcorrect
You need to put a plane as translucent material with your texture and add this shader to corona rayswitch material (it is better for complex scenes). Then, simply put the light source behind of your translucent plane with smaller area (like in real life), or, when you need to see the seperete shadows around each Led - try to make a plane, divide it to small pieces (led crystals) and apply corona light to it.
2. Tricky
Apply the corona light material to your plane with corona AO mask. This will give you control of darkening the edges.
If you need more explanations with images and results - feel free to write me
P.S. Cheers from Witten ;)