Please watch this video for more information and to see them in action: https://youtu.be/2W8YSOQ2y48
This is a 3D printed snowflake that will fit right over top of your string lights (like on a christmas tree for example). I think the bulbs on those are pretty standard sizes. These should scale so you can fit them to just about any light shaped like that if you want. And if you use clear filament, they'll light up really nicely. This is the clear filament I use: http://www.amazon.com/HATCHBOX-Transparent-3D-Printer-Filament/dp/B00M0CS8N2/ref=sr_1_1
These take about 20 minutes to print each. I can print a batch of 3 in an hour. They should fit without needing any adhesive or other attachment. They will print with no support material. I printed them at 0.3mm layer height.