Anyway, I had mixed results. The silicone held up very well, the mix of black and clear "shaped" the light into something almost perceptible, but the process was WAY messier than I expected. Silicone as it's curing has a personality. The second you aren't squirting a thin line of it into a crack and using a piece of plastic to swipe-shape it, well, it doesn't like to be puddled onto something and it definitely does't like you trying to draw with it. I also discovered you HAVE to do the clear and the black simultaneously because if you do the clear as a base layer then try to add the black over it they won't adhere.
My process was basically making a loop out of some string LEDs with all the individual LEDs facing inwards then covering it in clear silicone then quickly adding a border and top coat in the shape I wanted in black to try to make a glowing shape, namely a paw print.

I should have worked to spread the LEDs more evenly so the light was more even, and the surface texture definitely leaves something to be desired (though the addition of playa dust definitely helps). All in all it worked well. I was considering redoing it for this year, but I just didn't have the project time to spare when I was working my last job (today's the first day I'm not working 12+ hours in months).